Olefin copolymers containing hydrolytically cleavable linkages and use thereof in degradable products

ABSTRACT

The invention is directed to olefin copolymers composed of nonhydrolyzable monomer units and hydrolyzable monomer units, the latter resulting from copolymerization of monomers containing a linkage that is hydrolytically cleavable in the presence of aqueous base or aqueous acid. Generally, the hydrolyzable monomer units represent a significant fraction of the copolymer, such that upon hydrolysis, a substantial portion of the copolymer is degraded into low molecular weight fragments. Also provided are degradable articles that are at least partially composed of a degradable copolymer in which hydrolyzable monomer units represent at least 20 mole % of the copolymer. These degradable articles include agricultural film products, adhesive tape substrates, bed linens, containers, disposable absorbent articles, packaging materials, bags, labels, pillow cases, protective clothing, surgical drapes, sponges, tampon applicators, disposable syringes, temporary enclosures and temporary siding, toys, wipes, foamed plastic products, and controlled release pellets, strips and tabs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 10/392,270,filed Mar. 18, 2003 now U.S. Pat. No. 7,037,992, which is acontinuation-in-part of U.S. patent application Ser. No. 09/900,597,filed Jul. 6, 2001, now U.S. Pat. No. 6,534,610, which is a divisionalof U.S. patent application Ser. No. 09/408,286, filed Sep. 29, 1999, nowU.S. Pat. No. 6,288,184. The disclosures of the aforementionedapplications are incorporated by reference in their entireties.

TECHNICAL FIELD

This invention relates generally to olefin copolymers, and moreparticularly pertains to olefin copolymers containing hydrolyticallycleavable linkages, and to methods for synthesizing and using suchcopolymers. The invention additionally relates to recyclable productscomposed of olefin copolymers containing linkages that arehydrolytically cleavable at an acidic and/or basic pH. The invention hasutility in a variety of fields, including not only polymer chemistry perse, but also in the recycling and waste disposal industries, and inthose areas of manufacture in which recyclable products are desirable.

BACKGROUND

While a number of biodegradable polymers have been found to possess thedesirable characteristics of biodegradability and compostability, theyoften lack additional properties that are desired or necessary toprovide more commercially acceptable products. At room temperature manybiodegradable polymers are either too brittle to provide the desiredpuncture and tear resistance necessary for many applications, or they donot have adequate stability for storage and transport. In addition, manybiodegradable polymers are difficult to process into films usingcommercial manufacturing lines.

In attempts to overcome such difficulties, blends of polymeric materialswith other polymers or with naturally biodegradable components have beenattempted in efforts to develop thermoplastic films with improveddegradable properties. For example, U.S. Pat. No. 4,133,784 to Otey etal. describes degradable mulch films with improved moisture resistanceprepared from starch and ethylene/acrylic acid copolymers. U.S. Pat. No.5,091,262 to Knott et al. describes a multilayer polyethylene filmcontaining a starch filled inner layer, and prodegradant filled outerlayers. U.S. Pat. No. 5,108,807 to Tucker describes a multilayerthermoplastic film having a core layer made of polyvinyl alcohol, andouter layers made of polyethylene and prodegradant. U.S. Pat. No.5,391,423 to Wnuk et al. describes multilayer films prepared fromvarious biodegradable polymers for use in disposable absorbent products,such as diapers, incontinent pads, sanitary napkins, and pantyliners.

Typical, non-degradable or slowly degradable plastic products in theform of sheets and films (e.g., as in plastic trash bags and packagewrapping materials) are made primarily from hydrocarbon polymers such aspolyethylene, polypropylene, or polyvinyl polymers. The combination ofsuch hydrocarbon polymers with starch has not been very widely accepted.For example, trash bags incorporating starch with other hydrocarboncomponents can be physically degradable, which means they are brokeninto many small parts as the starch biodegrades. See, for example, U.S.Pat. No. 4,016,117 to Griffin, and U.S. Pat. No. 4,337,181 to Otey etal. See also Pettijohn (1992), “Starch/Polyolefin Blends asEnvironmentally Degradable Plastics,” Chemtech, 627; Willett (1994) J.Appl. Polym. Sci. 54:1685-1695. Initially, the starch particles exposedat, or adjacent to the surface of these starch-containing products, areinitially biodegraded and leached away. This is followed by successivebiodegradation of starch particles at the interior of the product toprovide a cellular structure that is more readily attacked by theprocesses of oxidation, hydrolysis, direct enzyme action or combinationsof these processes. However, such starch-containing products still leavebehind a non-biodegradable polymer residue as recognized in the art, forexample by U.S. Pat. No. 5,219,646 to Gallagher et al. The hydrocarboncomponents remain resistant to degradation and to mineralization. Incertain circumstances, it is believed that the hydrocarbon componenteven has a tendency to encapsulate the starch and thereby preventingfurther biodegradation of the starch. Furthermore, materialsincorporating large amounts of starch can be very sensitive to moistureand can have mechanical properties that vary considerably with humiditylevels. Accordingly, improved polymeric compositions for making betterbiodegradable films are needed.

There is also a need for degradable fibers that can be widely usedwithout polluting the environment. Such improved fibers are needed asfishing materials, such as fishing lines and fish nets; in agriculturalmaterials such as insect or bird nets and as vegetation nets; in clothfibers and non-woven fibers for articles for everyday life; in personalcare products such as diapers, incontinence pads, sanitary napkins,pantyliners, tampons, and diapers; and in medical supplies such asoperating sutures that are not removed, operating nets andsuture-reinforcing materials. Fibers that are degradable by the actionof microorganisms have been described. Examples of such fiberscomprising lactones or polyester fibers are described in U.S. Pat. No.6,235,393 to Kimura et al. However, such fibers are difficult and/orexpensive to manufacture while maintaining quality control, and someproducts are difficult to use due to insufficient flexibility. Arecently popular form of fiber made from synthetic polymers is referredto as “bicomponent” fibers. A bicomponent fiber comprises a core fibermade from one polymer that is encased within a thermoplastic sheath madefrom a different polymer. The polymer comprising the sheath often meltsat a different, typically lower, temperature than the polymer comprisingthe core. As a result, such bicomponent fibers can provide thermalbonding by controlled melting of the sheath polymer, while retaining thedesirable strength characteristics of the core polymer. An outer sheathis typically comprised of polyethylene, polypropylene, certainpolyesters, and the like, that often have softening and/or meltingpoints in the range of about 50° C. to about 200° C. Generally, however,such fibers are still difficult and/or expensive to manufacture.

There are a number of other polymer-based products for whichdegradability and/or compostability would be desirable. For example,films and laminates that are used in packaging materials, as topsheetsand backsheets in diapers, and as agricultural ground coverings areintended to survive intact for only a short period of use. Otherpolymer-based products for which degradability is desirable are moldedarticles such as tampon applicators, disposable syringes, milk bottles,shopping bags, food wrappers, beverage “six-pack” rings, and the like.Ideally, such molded articles would be substantially degraded in thesewage system or septic tank, or would decompose at the site of disposalso as to avoid causing visual litter problems or hazards to wildlife.

Plastic film products for agricultural mulching are representative ofthe problems that can be caused by the persistence of syntheticpolymers. Polyethylene is the most common polymer used in makingagricultural mulch products, and blends with starch have similardrawbacks to those described above for trash bag containers. Likeflexible film products for packaging and garbage bags, such agriculturalmulch products can persist for many years and become a nuisance. Thereis a need for plastic mulch products that can decompose by the end of agrowing season. Improved degradability would also be desirable toprovide items for “controlled release” of active agents from otheragricultural products, such as encapsulated pesticides, herbicides, andfertilizers.

Several approaches to enhance the environmental degradability ofpolymers have been suggested and tried. Photosensitizing groups havebeen added into the molecular structure of the polymer, and smallamounts of selective additives have been incorporated to accelerateoxidative and/or photo-oxidative degradation. However, photodegradationonly works well if the plastic is exposed to light, and provides nobenefit if the product is disposed of in a dark environment such asground water, soil or a standard landfill. Also, oxidative acceleratorscan cause unwanted changes in the mechanical properties of the polymer,such as embrittlement, prior to or during use.

Another approach to environmental degradability of articles made withsynthetic polymers is to make the polymer itself biodegradable orcompostable. See Swift (1993) Acc. Chem. Res. 26:105-110 for a generaloverview on biodegradable polymeric compositions. Most of this work hasbeen based on hydrolyzable polyester compositions, chemically modifiednatural polymers such as cellulose or starch or chitin, certainpolyamides, or blends thereof. See, for example, U.S. Pat. No. 5,219,646to Gallagher et al.(blend of hydrolyzable polyester and starch).Polyvinyl alcohol is the only synthetic high molecular weight additionpolymer with no heteroatom in the main chain generally acknowledged asbiodegradable, but consistent polymeric production is difficult. Seealso Hocking (1992) J. Mat. Sci. Rev. Macromol. Chem. Phys. C32(1):35-54, Cassidy et al. (1981) J. Macromol. Sci.—Rev. Macromol. Chem.C21(1):89-133, and “Encyclopedia of Polymer Science and Engineering,”2nd. ed.; Wiley & Sons: New York, 1989; Vol. 2, p220. (Limited reportsadd poly (alkyl 2-cyanoacrylates) to this list of biodegradablesynthetic polymers.)

Natural rubber (cis-1,4-polyisoprene) is also readily biodegradable.Natural rubber retains carbon-carbon double bonds in the polymerbackbone, which are believed to facilitate attack by either oxygenand/or microbes/fungi, leading subsequently to chain scission, molecularweight reduction, and eventually total degradation of the polymer. SeeHeap et al. (1968) J. Appl. Chem. 18:189-194. The precise mechanism forthe biodegradation of natural rubber is not known. Enzymatic and/oraerobic oxidation of the allylic methyl substituent may be involved. SeeTsuchii et al. (1990) Appl. Env. Micro., 269-274, Tsuchii et al. (1979)Agric. Biol. Chem. 43(12): 2441-2446, and Heap et al., supra. Bycontrast, nonbiodegradable polymers such as polyethylene, polypropylene,polyvinyl chloride, polyacrylonitrile, poly(meth)acrylates andpolystyrene have saturated carbon-carbon backbones that do notfacilitate attack by either oxygen and/or microbes. Thisbiodegradability has been recognized only for the natural form ofrubber.

Unfortunately, natural rubber is biodegradable to the extent that it istoo unstable for most uses. Natural rubber also suffers from poormechanical properties (e.g., strength, creep resistance). Indeed,stabilizers, fillers, and/or crosslinking agents are routinely added tonatural rubber to enhance its mechanical properties. Crosslinkers aretypically required in order to provide sufficient mechanical integrityfor practical use. However, the most common crosslinking process createsa polysulfide linkage, i.e., by vulcanization, that virtually eliminatesthe biodegradability of natural rubber. See Tsuchii et al. (1990) J.Appl. Polym. Sci. 41:1181-1187. Crosslinked natural rubber is alsoelastomeric and thermosetting, thus making it unsuitable for blown orextruded films, injection molded articles, fibers or othermelt-processed articles.

It would be desirable to provide polymer-containing products that: (1)are biodegradable in the environment, as well as degradable orcompostable during municipal waste handling operations; (2) arethermoplastic so that they can be molded, cast, extruded, or otherwisemelt-processed into various forms including films, fibers, coatings,foams, and the like; (3) can be manufactured at reasonable cost; and (4)have sufficient toughness, strength and stability during use until theyare appropriately disposed of. Therefore, polymers or copolymers areneeded that provide reproducible and predictable properties with respectto degradation and environmental hydrolysis, and that hydrolyze to avery significant extent to provide small, soluble, and generallynontoxic polymer fragments.

For many purposes, the superior physical properties provided bypolyolefins prepared by addition polymerization are desirable. To date,however, the incorporation of polar moieties, e.g., hydrolyzable polarlinkages, into such polymers has had limited success, since many polarmonomers poison, or competitively coordinate with, the organometallicpolymerization catalysts that are typically used. Copolymers of olefins,such as ethylene, with polar monomers such as acrylates, were initiallylimited to block copolymers, formed by two-stage polymerization, e.g.,by post-polymerization of an acrylate or methacylrate monomer onto apreviously formed polyolefin chain. See U.S. Pat. No. 5,563,219 toYasuda et al., EP 0799842 to Yasuda et al., EP 0462588 to Goto et al.,and EP 0442476 to Hajime et al. JP Kokai 4-45108 pertains to thepreparation of an ethylene copolymer containing 4.7 mole % ethylacrylate (number average molecular weight M_(n) of 9,100, weight averagemolecular weight M_(w) of 22,500) that is described as exhibitingimproved adhesion relative to homopolymeric polyethylene. Johnson et al.(1996), J. Am. Chem. Soc. 118:267-8, described the formation of randomolefin-acrylate copolymers using Brookhart-type catalysts. None of thesepolymers, however, include hydrolyzable linkages in the backbone of thepolymer, and therefore they would not be hydrolytically degradable.

Ouchi et al. (1968), J. Chem. Soc. Japan 71(7):1078-82, described freeradical copolymerization of styrene and other vinyl monomers with amonomer containing a hydrolyzable linkage, diallylidene pentaerythritol(DAPE). However, the process resulted in a copolymer (1) in whichrelatively little hydrolyzable monomer was incorporated, or (2)exhibiting a significant loss in intrinsic viscosity at higher levels ofincorporation. Higher levels of hydrolyzable monomer incorporation werealso found to be associated with a lower polymerization rate.Additionally, the reaction conditions employed would be expected toresult in a non-stereoregular polymer.

Austin et al., in International Patent Publication No. WO 92/12185,describes a method for making biodegradable and photodegradable polymerscontaining ester linkages. The disclosed polymerization method involvesa radical-initiated ring-opening copolymerization reaction betweenethylene and a cyclic ketene acetal, 2-methylene-1,3-dioxepane (MDOP).The resulting copolymer contains both ethylene monomer units (—CH₂—CH₂—)and ester-containing monomer units having the structure —(CO)—O—(CH₂)₄—.The maximum amount of the ester-containing monomer units incorporatedinto the copolymer, however, was only 3.20 mole %, even when the amountof MDOP in the feed was increased to 25 wt. %. Such a copolymer wouldhydrolyze to a very limited extent and be of minimal utility inproviding degradable products.

SUMMARY OF THE INVENTION

The invention is directed, in part, to a olefin copolymer that isdegradable by virtue of being hydrolyzable in the presence of aqueousbase or aqueous acid. The copolymer comprises both nonhydrolyzablemonomer units and hydrolyzable monomer units, the latter being“hydrolyzable” by virtue of containing at least one linkage that ishydrolytically cleavable under acidic or basic conditions.

In one aspect, the invention provides such a copolymer wherein:

(a) the nonhydrolyzable monomer units result from polymerization ofnonhydrolyzable olefin monomers; and

(b) the hydrolyzable monomer units result from polymerization ofhydrolyzable olefin monomers containing at least one linkage that ishydrolytically cleavable under acidic or basic conditions, wherein thelinkage is selected from enol ether, acyclic acetal, hemiacetal,anhydride, carbonate, N-substituted amido, N-substituted urethane,N-substituted imino, imido, substituted imido, N,N-disubstitutedhydrazo, thioester, phosphonic ester, sulfonic ester, ortho ester,ether, thio, and siloxyl.

As one example, the nonhydrolyzable monomer units are of the form—R¹CH—CHR²—, resulting from copolymerization of a monomer having thestructure R¹CH═CHR² in which R¹ is hydrido, C₁-C₂₄ alkyl, substitutedC₁-C₂₄ alkyl, C₁-C₂₄ heteroalkyl, or substituted C₁-C₂₄ heteroalkyl, andR² is hydrido, C₁-C₂₄ alkyl, substituted C₁-C₂₄ alkyl, C₁-C₂₄heteroalkyl, substituted C₂-C₂₄ heteroalkyl, C₂-C₂₄ alkenyl, substitutedC₂-C₂₄ alkenyl, C₂-C₂₄ heteroalkenyl, substituted C₂-C₂₄ heteroalkenyl,C₅-C₂₄ aryl, substituted C₅-C₂₄ aryl, C₅-C₂₄ heteroaryl, substitutedC₅-C₂₄ heteroaryl, C₆-C₂₄ alkaryl, substituted and/orheteroatom-containing C₆-C₂₄ alkaryl, or halo, or wherein R¹ and R² arelinked to form a cyclic group, typically a five- to eight-membered ring(including the two olefinic carbon atoms to which R¹ and R² are directlybound). The second monomer unit is hydrolyzable and of the form—CHR³—CH₂-(L¹)_(m)-X-(L²)_(n)-CH₂—CHR⁴ — and results fromcopolymerization of a monomer having the structureR³CH═CH-(L¹)_(m)-X-(L²)_(n)-CH═CHR⁴ in which R³ and R⁴ are independentlyhydrido, C₁-C₂₄ alkyl, substituted C₁-C₂₄ alkyl, C₁-C₂₄ heteroalkyl,substituted C₁-C₂₄ heteroalkyl, C₅-C₂₄ aryl, substituted C₅-C₂₄ aryl,C₅-C₂₄ heteroaryl, or substituted C₅-C₂₄ heteroaryl, X is the linkagethat is hydrolytically cleavable at an acidic or basic pH, L¹ and L² areoptionally substituted and/or heteroatom-containing hydrocarbylenegroups, and may contain an additional hydrolytically cleavable linkage,and m and n are independently 0 or 1. The amount of the second monomerunit in the copolymer generally ranges from about 15 mole % to about 75mole %.

In a related aspect, the invention provides a degradable olefincopolymer prepared by addition polymerization, in the presence of acatalytically effective amount of a transition metal complex and acatalyst activator that renders the complex cationic or zwitterionic, ofa monomer mixture containing: at most 80 mole % of at least onenonhydrolyzable monomer of the form R¹CH═CHR², wherein R¹ is hydrido orC₁-C₂₄ alkyl, and R² is hydrido, alkyl, alkenyl, aryl, alkaryl, or halo,or where R¹ and R² taken together form a hydrocarbylene linkage; and atleast 20 mole % of a hydrolyzable monomer of the formR³CH═CH-(L¹)_(m)-X-(L²)_(n)-CH═CHR⁴ wherein R³ and R⁴ are independentlyhydrido, alkyl, aryl or substituted aryl, L¹ and L² are optionallysubstituted and/or heteroatom-containing hydrocarbylene groups, m and nare independently 0 or 1, and X is a hydrolytically cleavable linkage,

wherein the transition metal complex is selected from a metallocenecomplex of a Group 4, 5, or 6 transition metal and a 1,2-diimine complexof a Group 8 transition metal or an analog thereof.

In an exemplary such embodiment, a degradable olefin copolymer isprovided that is prepared by addition polymerization, in the presence ofa catalytically effective amount of a metallocene complex of a Group 4,5, or 6 transition metal and a catalyst activator that renders thecomplex cationic or zwitterionic, of a monomer mixture containing atmost 80 mole % of at least one nonhydrolyzable olefin monomer and atleast 20 mole % of a diolefin monomer containing a hydrolyticallycleavable linkage selected from a cyclic acetal linkage and an esterlinkage.

The invention also pertains to a polymer blend that contains at leastone degradable olefin copolymer of the invention and at least oneadditional polymer. The at least one additional polymer may be anadditional degradable polymer, e.g., a hydrolytically, photolytically,or enzymatically degradable polymer, and/or a nondegradable polymer. Inone embodiment, the blend contains about 5 wt. % to about 99 wt. % of amixture of degradable polymers and about 1 wt. % to 95 wt. % of anondegradable polymer, wherein the mixture of degradable polymers iscomposed of about 30 wt. % to about 95 wt. % of a copolymer of theinvention and about 5 wt. % to about 70 wt. % of at least one additionaldegradable polymer.

In a further aspect, the invention provides a degradable article that atleast partially comprises a degradable copolymer composed of at most 80mole % of nonhydrolyzable monomer units resulting from polymerization ofnonhydrolyzable olefin monomers, and at least 20 mole % of hydrolyzablemonomer units resulting from polymerization of hydrolyzable olefinmonomers containing at least one linkage that is hydrolyticallycleavable under acidic or basic conditions. The article is generallyselected from films, fibers, foams, woven fabrics, nonwoven fabrics, andmolded articles. Examples of specific articles include, withoutlimitation: agricultural film products; adhesive tape substrates; bedlinens; containers; coverings, e.g., backsheets and topsheets, fordisposable absorbent articles; packaging materials; bags; labels; pillowcases; protective clothing; surgical drapes; sponges; tamponapplicators; disposable syringes; temporary enclosures and temporarysiding; toys; wipes; foamed plastic products; and controlled releasepellets, strips and tabs. Disposable adhesive articles include, withoutlimitation, diapers, sanitary napkins, incontinence pads, pantyliners,and disposable training pants. A preferred degradable copolymer used forthe fabrication of these degradable articles is a copolymer of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are NMR spectra of3,9-divinyl-2,4,8,10-tetraoxaspiro[5,5]undecane (a hydrolyzable monomer)and its copolymer with ethylene, respectively, as described in Example1.

FIG. 3 is a graph of hydrolysis data showing the percentage of dissolvedpolymer relative to pH as described in Example 7 for the copolymer ofExample 1.

DETAILED DESCRIPTION OF THE INVENTION

I. Difinitions and Nomenclature

It is to be understood that unless otherwise indicated this invention isnot limited to specific reactants, reaction conditions, ligands, metalcomplexes, or the like, as such may vary. It is also to be understoodthat the terminology used herein is for the purpose of describingparticular embodiments only and is not intended to be limiting. Unlessotherwise indicated, this invention is not limited to specific monomers,polymers, catalysts, hydrolysis conditions, or the like, as such mayvary. The terminology used herein is for the purpose of describingparticular embodiments only and is not intended to be limiting.

As used in the specification and the appended claims, the singular forms“a,” “an,” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to “a monomer”encompasses a combination or mixture of different polymers as well as asingle polymer, reference to “a catalyst” encompasses both a singlecatalyst as well as two or more catalysts used in combination, and thelike.

In this specification and in the claims that follow, reference will bemade to a number of terms, which shall be defined to have the followingmeanings:

As used herein, the phrase “having the formula” or “having thestructure” is not intended to be limiting and is used in the same waythat the term “comprising” is commonly used.

The term “alkyl” as used herein refers to a linear, branched or cyclicsaturated hydrocarbon substituent that generally although notnecessarily contains 1 to about 24 carbon atoms, such as methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl, and thelike, as well as cycloalkyl groups such as cyclopentyl, cyclohexyl andthe like. Generally, although again not necessarily, alkyl groups hereincontain 1 to about 12 carbon atoms. The term “lower alkyl” intends analkyl group of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Theterm “substituted alkyl” refers to alkyl substituted with one or moresubstituent groups, i.e., wherein a hydrogen atom is replaced with anon-hydrogen substituent group, and the terms “heteroatom-containingalkyl” and “heteroalkyl” refer to alkyl substituents in which at leastone carbon atom is replaced with a heteroatom. If not otherwiseindicated, the terms “alkyl” and “lower alkyl” include linear, branched,cyclic, unsubstituted, substituted, and/or heteroatom-containing alkyland lower alkyl, respectively.

The term “alkylene” as used herein refers to a difunctional linear,branched, or cyclic saturated hydrocarbon linkage, typically althoughnot necessarily containing 1 to about 24 carbon atoms, such asmethylene, ethylene, n-propylene, n-butylene, n-hexylene, decylene,tetradecylene, hexadecylene, and the like. Preferred alkylene linkagescontain 1 to about 12 carbon atoms, and the term “lower alkylene” refersto an alkylene linkage of 1 to 6 carbon atoms, preferably 1 to 4 carbonatoms. The term “substituted alkylene” refers to an alkylene linkagesubstituted with one or more substituent groups, i.e., wherein ahydrogen atom is replaced with a non-hydrogen substituent group, and theterms “heteroatom-containing alkylene” and “heteroalkylene” refer toalkylene linkages in which at least one carbon atom is replaced with aheteroatom. If not otherwise indicated, the terms “alkylene” and “loweralkylene” include linear, branched, cyclic, unsubstituted, substituted,and/or heteroatom-containing alkylene and lower alkylene, respectively.

The term “alkenyl” as used herein refers to a linear, branched, orcyclic hydrocarbon group of 2 to about 24 carbon atoms containing atleast one double bond, such as ethenyl, n-propenyl, isopropenyl,n-butenyl, isobutenyl, octenyl, decenyl, tetradecenyl, hexadecenyl,eicosenyl, tetracosenyl, and the like. Preferred alkenyl groups hereincontain 2 to about 12 carbon atoms. The term “lower alkenyl” intends analkenyl group of 2 to 6, preferably 2 to 4 carbon atoms, and thespecific term “cycloalkenyl” intends a cyclic alkenyl group, preferablyhaving 5 to 8 carbon atoms. The term “substituted alkenyl” refers toalkenyl substituted with one or more substituent groups, and the terms“heteroatom-containing alkenyl” and “heteroalkenyl” refer to alkenyl inwhich at least one carbon atom is replaced with a heteroatom. If nototherwise indicated, the terms “alkenyl” and “lower alkenyl” includelinear, branched, cyclic, unsubstituted, substituted, and/orheteroatom-containing alkenyl and lower alkenyl, respectively.

The term “alkenylene” as used herein refers to a difunctional linear,branched, or cyclic alkenyl group, where “alkenyl” is as defined above.The term “alkenylene” as used herein refers to a difunctional linear,branched, or cyclic hydrocarbon linkage containing at least onecarbon-carbon double bond, typically although not necessarily containing2 to about 24 carbon atoms, such as ethylene, n-propylene, n-butylene,n-hexylene, decylene, tetradecylene, hexadecylene, and the like.Preferred alkenylene linkages contain 2 to about 12 carbon atoms, andthe term “lower alkenylene” refers to an alkenylene linkage of 2 to 6carbon atoms, preferably 2 to 4 carbon atoms. The term “substitutedalkenylene” refers to an alkenylene linkage substituted with one or moresubstituent groups, i.e., wherein a hydrogen atom is replaced with anon-hydrogen substituent group, and the terms “heteroatom-containingalkenylene” and “heteroalkenylene” refer to alkenylene linkages in whichat least one carbon atom is replaced with a heteroatom. If not otherwiseindicated, the terms “alkenylene” and “lower alkenylene” include linear,branched, cyclic, unsubstituted, substituted, and/orheteroatom-containing alkenylene and lower alkenylene, respectively.

The term “alkoxy” as used herein refers to an alkyl group bound througha single, terminal ether linkage; that is, an “alkoxy” group may berepresented as —O-alkyl where alkyl is as defined above. A “loweralkoxy” group refers to an alkoxy group containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, and includes, for example, methoxy,ethoxy, n-propoxy, isopropoxy, t-butyloxy, etc. If not otherwiseindicated, the terms “alkoxy” and “lower alkoxy” include linear,branched, cyclic, unsubstituted, substituted, and/orheteroatom-containing alkoxy and lower alkoxy groups, respectively.

The term “aryl” as used herein, and unless otherwise specified, refersto an aromatic substituent containing a single aromatic ring or multiplearomatic rings that are fused together, directly linked, or indirectlylinked (such that the different aromatic rings are bound to a commongroup such as a methylene or ethylene moiety). Preferred aryl groupscontain 5 to 24 carbon atoms and either one aromatic ring or 2 to 4fused or linked aromatic rings, e.g., phenyl, naphthyl, biphenyl, andthe like, with more preferred aryl groups containing 1 to 3 aromaticrings, and particularly preferred aryl groups containing 1 or 2 aromaticrings and 5 to 14 carbon atoms. “Substituted aryl” refers to an arylmoiety substituted with one or more substituent groups, and the terms“heteroatom-containing aryl” and “heteroaryl” refer to an aryl group inwhich at least one ring carbon atom is replaced with a heteroatom.Unless otherwise indicated, the term “aryl” includes substituted and/orheteroaryl species.

The term “aryloxy” as used herein refers to an aryl group bound througha single, terminal ether linkage, wherein “aryl” is as defined above. An“aryloxy” group may be represented as —O-aryl where aryl is as definedabove. Preferred aryloxy groups contain 5 to 24 carbon atoms, andparticularly preferred aryloxy groups contain 5 to 14 carbon atoms.Examples of aryloxy groups include, without limitation, phenoxy,o-halo-phenoxy, m-halo-phenoxy, p-halo-phenoxy, o-methoxy-phenoxy,m-methoxy-phenoxy, p-methoxy-phenoxy, 2,4-dimethoxy-phenoxy,3,4,5-trimethoxy-phenoxy, and the like.

The term “alkaryl” refers to an aryl group with an alkyl substituent,and the term “aralkyl” refers to an alkyl group with an arylsubstituent, wherein “aryl” and “alkyl” are as defined above. Preferredaralkyl groups contain 6 to 24 carbon atoms, and particularly preferredaralkyl groups contain 6 to 16 carbon atoms. Examples of aralkyl groupsinclude, without limitation, benzyl, 2-phenyl-ethyl, 3-phenyl-propyl,4-phenyl-butyl, 5-phenyl-pentyl, 4-phenylcyclohexyl, 4-benzylcyclohexyl,4-phenylcyclohexylmethyl, 4-benzylcyclohexylmethyl, and the like.Alkaryl groups include, for example, p-methylphenyl, 2,4-dimethylphenyl,p-cyclohexylphenyl, 2,7-dimethylnaphthyl, 7-cyclooctylnaphthyl,3-ethyl-cyclopenta-1,4-dienyl, and the like.

The term “halo” is used in the conventional sense to refer to a chloro,bromo, fluoro or iodo substituent.

“Hydrocarbyl” refers to univalent hydrocarbyl radicals containing 1 toabout 24 carbon atoms, most preferably 1 to about 12 carbon atoms,including linear, branched, cyclic, saturated and unsaturated species,such as alkyl groups, alkenyl groups, aryl groups, and the like. Theterm “lower hydrocarbyl” intends a hydrocarbyl group of 1 to 6 carbonatoms, preferably 1 to 4 carbon atoms. The term “hydrocarbylene” intendsa divalent hydrocarbyl moiety containing 1 to about 24 carbon atoms,most preferably 1 to about 12 carbon atoms, including linear, branched,cyclic, saturated and unsaturated species, and the term “lowerhydrocarbylene” intends a hydrocarbylene group of 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms. The term “substituted hydrocarbyl”refers to hydrocarbyl substituted with one or more substituent groups,and the terms “heteroatom-containing hydrocarbyl” and“heterohydrocarbyl” refer to hydrocarbyl in which at least one carbonatom is replaced with a heteroatom. Similarly, “substitutedhydrocarbylene” refers to hydrocarbylene substituted with one or moresubstituent groups, and the terms “heteroatom-containing hydrocarbylene”and “heterohydrocarbylene” refer to hydrocarbylene in which at least onecarbon atom is replaced with a heteroatom. Unless otherwise indicated,the terms “hydrocarbyl” and “hydrocarbylene” are to be interpreted asincluding substituted and/or heteroatom-containing hydrocarbyl andhydrocarbylene moieties, respectively.

The term “heteroatom-containing” as in a “heteroatom-containinghydrocarbyl group” refers to a hydrocarbon molecule or a hydrocarbylmolecular fragment in which one or more carbon atoms is replaced with anatom other than carbon, e.g., nitrogen, oxygen, sulfur, phosphorus orsilicon, typically nitrogen, oxygen or sulfur. Similarly, the term“heteroalkyl” refers to an alkyl substituent that isheteroatom-containing, the term “heterocyclic” refers to a cyclicsubstituent that is heteroatom-containing, the terms “heteroaryl” andheteroaromatic” respectively refer to “aryl” and “aromatic” substituentsthat are heteroatom-containing, and the like. It should be noted that a“heterocyclic” group or compound may or may not be aromatic, and furtherthat “heterocycles” may be monocyclic, bicyclic, or polycyclic asdescribed above with respect to the term “aryl.”

By “substituted” as in “substituted alkyl,” “substituted aryl,” and thelike, as alluded to in some of the aforementioned definitions, is meantthat in the alkyl, aryl, or other moiety, at least one hydrogen atombound to a carbon (or other) atom is replaced with one or morenon-hydrogen substituents. Examples of such substituents include,without limitation: functional groups such as halo, hydroxyl,sulfhydryl, C₁-C₂₄ alkoxy (preferably C₁-C₁₂ alkoxy, more preferablyC₁-C₆ alkoxy), C₅-C₂₄ aryloxy (preferably C₅-C₁₄ aryloxy), acyl(including C₂-C₂₄ alkylcarbonyl (—CO-alkyl) and C₆-C₂₄ arylcarbonyl(—CO-aryl), preferably C₂-C₁₂ alkylcarbonyl and C₆-C₁₆ arylcarbonyl, andmost preferably C₂-C₆ alkylcarbonyl), acyloxy (—O-acyl), C₂-C₂₄,preferably C₂-C₁₂, and most preferably C₂-C₆ alkoxycarbonyl(—(CO)—O-alkyl), C₆-C₂₄, preferably C₆-C₁₄ aryloxycarbonyl(—(CO)—O-aryl), halocarbonyl (—CO)—X where X is halo), carboxy (—COOH),carboxylato (—COO⁻), carbamoyl (—(CO)—NH₂), mono-(C₁-C₂₄, preferablyC₁-C₁₂ alkyl, most preferably C₁-C₆ alkyl)-substituted carbamoyl(—(CO)—NH(alkyl)), di-(C₁-C₂₄, preferably C₁-C₁₂ dialkyl, mostpreferably C₁-C₆ dialkyl)-substituted carbamoyl (—(CO)—N(alkyl)₂),mono-(C₅-C₂₄, preferably C₅-C₁₄ aryl)-substituted carbamoyl(—(CO)—NH-aryl), di-(C₅-C₂₄, preferably C₅-C₁₄ aryl)-substitutedcarbamoyl (—(CO)—N(aryl)₂), di-N-(C₁-C₂₄, preferably C₁-C₁₂ alkyl, mostpreferably C₁-C₆ alkyl), N—(C₅-C₂₄, preferably C₅-C₁₄ aryl)-substitutedcarbamoyl, thiocarbamoyl (—(CS)—NH₂), carbamido (—NH—(CO)—NH₂), formyl(—(CO)—H), thioformyl (—(CS)—H), amino (—NH₂), mono-(C₁-C₂₄, preferablyC₁-C₁₂ alkyl, most preferably C₁-C₆ alkyl)-substituted amino,di-(C₁-C₂₄, preferably C₁-C₁₂ alkyl, most preferably C₁-C₆alkyl)-substituted amino, mono-(C₅-C₂₄, preferably C₅-C₁₄aryl)-substituted amino, di-(C₅-C₂₄, preferably C₅-C₁₄ aryl)-substituteamino, C₂-C₂₄, preferably C₂-C₁₂, most preferably C₂-C₆ alkylamido(—NH—(CO)-alkyl), C₅-C₂₄, preferably C₅-C₁₄ arylamido (—NH—(CO)-aryl),nitro (—NO₂), sulfo (—SO₂—OH), sulfonato (—SO₂—O⁻), C₁-C₂₄, preferablyC₁-C₁₂, most preferably C₁-C₆ alkylsulfanyl (—S-alkyl; also termed“alkylthio”), arylsulfanyl (—S-aryl; also termed “arylthio”), C₁-C₂₄,preferably C₁-C₁₂, most preferably C₁-C₆ alkylsulfinyl (—(SO)-alkyl),C₅-C₂₄, preferably C₅-C₁₄ arylsulfinyl (—(SO)-aryl), C₁-C₂₄, preferablyC₁-C₁₂, most preferably C₁-C₆ alkylsulfonyl (—SO₂-alkyl), C₅-C₂₄,preferably C₅-C₁₄ arylsulfonyl (—SO₂-aryl), phosphono (—P(O)(OH)₂),phosphonato (—P(O)(O⁻)₂), di(C₁-C₂₄, preferably C₁-C₁₂, most preferablyC₁-C₆)-alkyl phosphonyl (—P(O)(O-alkyl)₂), di(C₅-C₂₄, preferablyC₅-C₁₄)-aryl phosphonyl (—P(O)(O-aryl)₂), phosphinato (—P(O)(O⁻)),C₁-C₂₄, preferably C₁-C₁₂, most preferably C₁-C₆ alkyl phosphinyl(—P(O)(O-alkyl)), C₅-C₂₄, preferably C₅-C₁₄ arylphosphinyl(—P(O)(O-aryl)), phospho (—PO₂), and phosphino (—PH₂); and thehydrocarbyl moieties C₁-C₂₄ alkyl (preferably C₁-C₁₂ alkyl, morepreferably C₁-C₆ alkyl), C₂-C₂₄ alkenyl (preferably C₂-C₁₃ alkenyl, morepreferably C₂-C₆ alkenyl), C₂-C₂₄ alkynyl (preferably C₂-C₁₂ alkynyl,more preferably C₂-C₆ alkynyl), C₅-C₂₄ aryl (preferably C₅-C₁₄ aryl),C₆-C₂₄ alkaryl (preferably C₆-C₁₆ alkaryl), and C₆-C₂₄ aralkyl(preferably C₆-C₁₆ aralkyl).

In addition, the aforementioned functional groups may, if a particulargroup permits, be further substituted with one or more additionalfunctional groups or with one or more hydrocarbyl moieties such as thosespecifically enumerated above. Analogously, the above-mentionedhydrocarbyl moieties may be further substituted with one or morefunctional groups or additional hydrocarbyl moieties such as thosespecifically enumerated.

When the term “substituted” appears prior to a list of possiblesubstituted groups, it is intended that the term apply to every memberof that group. For example, the phrase “substituted alkyl, alkenyl, andaryl” is to be interpreted as “substituted alkyl, substituted alkenyl,and substituted aryl.” Analogously, when the term“heteroatom-containing” appears prior to a list of possibleheteroatom-containing groups, it is intended that the term apply toevery member of that group. For example, the phrase“heteroatom-containing alkyl, alkenyl, and aryl” is to be interpreted as“heteroatom-containing alkyl, substituted alkenyl, and substitutedaryl.”

The term “comonomer” in an addition polymerization refers to thehydrolyzable comonomer, unless otherwise indicated.

A “diene comonomer” is incorporated as a “chain extender” when bothdouble bonds are incorporated into the polymer backbone in a linearfashion, as opposed to incorporation as a crosslinker, wherein the twodouble bonds are incorporated into separate polymer chains.

The term “degradable” refers to a molecular segment, copolymer, orproduct that can be degraded by acid or base hydrolysis, by virtue of ahydrolytically cleavable linkage in the molecular segment, thecopolymer, or in a copolymer incorporated into the product.

The term “hydrolyzable” refers to a compound or molecular segment (e.g.,a monomer or monomer unit) containing a covalent chemical linkagebetween two atoms that is hydrolytically cleavable at an acidic or basicpH. It will be appreciated that a different pH will be necessary fordifferent types of compounds, and that certain compounds and linkagesare hydrolytically cleavable at a pH that is close to neutral (7.0)while other compounds and linkages may require a higher or lower pH forhydrolytic cleavage. As the present copolymers are intended for use indegradable products that are ultimately subject to waste disposalprocessing, including recycling, hydrolysis may be ensured by carryingout any post-disposal processing at a pH known to enable hydrolyticcleavage. If the products are disposed of in conventional ways notinvolving processing, they will hydrolyze as a result of naturalvariations in environmental pH. Additionally, the consumer mayfacilitate hydrolysis of certain types of products, e.g., by disposingof a diaper, sanitary napkin, incontinence pad, pantyliner, tampon, orthe like, in a toilet and adding a pH-adjusting compound to the waterprior to flushing. Preferred hydrolyzable linkages herein are basecleavable.

Conversely, “nonhydrolyzable” refers to a compound or molecular segment(e.g., a monomer or monomer unit) not containing a covalent chemicallinkage between two atoms that is hydrolytically cleavable at an acidicor basic pH.

A “heterogeneous” catalyst as used herein refers to a catalyst supportedon a carrier, typically although not necessarily a substrate comprisedof an inorganic, solid, particulate porous material such as siliconand/or aluminum oxide.

A “homogeneous” catalyst as used herein refers to a catalyst that is notsupported but is simply admixed with the initial monomeric components ina suitable solvent.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, the phrase “optionally substituted” means that anon-hydrogen substituent may or may not be present on a given atom, and,thus, the description includes structures wherein a non-hydrogensubstituent is present and structures wherein a non-hydrogen substituentis not present.

II. Degradable Olefin Copolymers

The present polymers may be used in a host of applications in whichdegradability, particularly hydrolyzability, is desirable or necessary.Potential applications are discussed in detail infra, in section IV.

The subject copolymers are hydrolytically degradable olefin copolymerswithout adjacent hydrolyzable monomers, comprising a first monomer unitthat is not hydrolyzable and a second monomer unit that is hydrolyzable.

The first monomer unit derives from a first addition polymerizablemonomer of the form CHR¹═CHR², wherein R¹ is hydrido, C₁-C₂₄ alkyl,substituted C₁-C₂₄ alkyl, C₁-C₂₄ heteroalkyl, or substituted C₁-C₂₄heteroalkyl, preferably hydrido or C₁-C₁₂ alkyl, most preferably hydridoor lower alkyl, and R² is hydrido, C₁-C₂₄ alkyl, substituted C₁-C₂₄alkyl, C₁-C₂₄ heteroalkyl, substituted C₁-C₂₄ heteroalkyl, C₂-C₂₄alkenyl, substituted C₂-C₂₄ alkenyl, C₂-C₂₄ heteroalkenyl, substitutedC₂-C₂₄ heteroalkenyl, C₅-C₂₄ aryl, substituted C₅-C₂₄ aryl, C₅-C₂₄heteroaryl, substituted C₅-C₂₄ heteroaryl, C₆-C₂₄ alkaryl, substitutedand/or heteroatom-containing C₆-C₂₄ alkaryl, or halo, preferablyhydrido, C₁-C₁₂ alkyl, substituted C₁-C₁₂ alkyl, C₁-C₁₂ heteroalkyl,substituted C₁-C₁₂ heteroalkenyl, C₂-C₁₂ alkenyl, substituted C₂-C₁₂alkenyl, C₂-C₁₂ heteroalkenyl, substituted C₂-C₁₂ heteroalkenyl, C₅-C₁₄aryl, substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl, substituted C₅-C₁₄heteroaryl, C₆-C₁₆ alkaryl, substituted and/or heteroatom-containingC₆-C₁₆ alkaryl, or halo, most preferably hydrido, lower alkyl,substituted lower alkyl, lower heteroalkyl, substituted lowerheteroalkyl, C₅-C₁₄ aryl, substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl,substituted C₅-C₁₄ heteroaryl, C₆-C₁₆ alkaryl, substituted and/orheteroatom-containing C₆-C₁₆ alkaryl, or halo, or wherein R¹ and R² arelinked to form a cyclic group, typically a five- to eight-membered ring(including the two olefinic carbon atoms to which R¹ and R² are directlybound). In such a case, the two olefinic carbon atoms will be linkedthrough a bridge -Q- wherein Q is hydrocarbylene and provides athree-atom to seven-atom spacer, wherein Q is optionally substitutedwith one or more substituents such as alkyl, aryl, alkoxy, halo, or thelike, and/or containing one or more heteroatoms such as O, S, or N.

Examples of such monomers include olefins having from about 2 to about20 carbon atoms, such as linear or branched olefins including ethylene,propylene, 1-butene, 3-methyl-1-butene, 1,3-butadiene, 1-pentene,4-methyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1,4-hexadiene,1,5-hexadiene, 1-octene, 1,6-octadiene, 1-nonene, 1-decene,1,4-dodecadiene, 1-hexadecene, 1-octadecene, and mixtures thereof.Cyclic olefins, diolefins, triolefins, tetraolefins, etc., may also beused; such compounds include, for example, cyclopentene,3-vinylcyclohexene, norbornene, 5-vinyl-2-norbornene,5-ethylidene-2-norbornene, dicyclopentadiene, 4-vinylbenzocyclobutane,tetracyclododecene, dimethano-octahydronaphthalene, and7-octenyl-9-borabicyclo-(3,3,1)nonane. Aromatic olefinic and vinylmonomers that may be polymerized using the present method include, butare not necessarily limited to, styrene, o-methylstyrene,m-methylstyrene, p-methylstyrene, p-tert-butylstyrene, m-chlorostyrene,p-chlorostyrene, p-fluorostyrene, indene, 4-vinylbiphenyl,acenaphthalene, vinylfluorene, vinylanthracene, vinylphenanthrene,vinylpyrene and vinylchrisene. Still other monomers that may bepolymerized within the context of the present method include methylmethacrylate, ethylacrylate, vinyl silane, phenyl silane, trimethylallylsilane, acrylonitrile, maleimide, vinyl chloride, vinylidene chloride,tetrafluoroethylene, isobutylene, carbon monoxide, acrylic acid,2-ethylhexylacrylate, methacrylonitrile, and methacrylic acid.

The second monomer unit derives from monomers having the structureCHR³═CH-(L¹)_(m)-X-(L²)_(n)-CH═CHR⁴ wherein R³, R⁴, L¹, L², m, n and Xare as defined below.

R³ and R⁴ are independently hydrido, C₁-C₂₄ alkyl, substituted C₁-C₂₄alkyl, C₁-C₂₄ heteroalkyl, substituted C₁-C₂₄ heteroalkyl, C₅-C₂₄ aryl,substituted C₅-C₂₄ aryl, C₅-C₂₄ heteroaryl, or substituted C₅-C₂₄heteroaryl, preferably hydrido, C₁-C₁₂ alkyl, substituted C₁-C₁₂ alkyl,C₁-C₁₂ heteroalkyl, substituted C₁-C₁₂ heteroalkyl, C₅-C₁₄ aryl,substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl, or substituted C₅-C₁₄heteroaryl, more preferably hydrido or lower alkyl, still morepreferably hydrido or methyl, and most preferably hydrido.

L¹ and L² are optionally substituted and/or heteroatom-containinghydrocarbylene groups, e.g., C₁-C₂₄ alkylene, substituted C₁-C₂₄alkylene, C₁-C₂₄ heteroalkylene, substituted C₁-C₂₄ heteroalkylene,C₂-C₂₄ alkenylene, substituted C₂-C₂₄ alkenylene, C₂-C₂₄heteroalkenylene, or substituted C₂-C₂₄ heteroalkenylene, preferablyC₁-C₁₂ alkylene, substituted C₁-C₁₂ alkylene, C₂-C₁₂ heteroalkylene, orsubstituted C₂-C₁₂ heteroalkylene, most preferably substituted orunsubstituted lower alkylene, and optimally unsubstituted loweralkylene. L¹ and/or L² may also contain a hydrolytically cleavablelinkage as explained below with respect to X. Further, when L¹ and/or L²is substituted, the substituent may be an alkenyl group, e.g., asubstituted or unsubstituted allyl moiety, and more than one suchsubstituent can be present on each of L¹ and L². Thus, the hydrolyzablemonomer may be a polyolefin, e.g., a triolefin or tetraolefin. Onerepresentative such monomer is tetraallyloxysilane,

The subscripts m and n are independently 0 or 1, such that L¹ and L² mayor may not be present.

X is a linkage that is hydrolytically cleavable under aqueousconditions, generally at acidic or basic pH. To prevent deactivation ofthe polymerization catalyst, X does not include a group containing anactive hydrogen atom, e.g., a hydroxyl group, a primary or secondaryamino group, or a thiol group, nor does it contain any group that couldoxidize the metal center of the catalyst. Preferred X linkages include,but are not limited to, the following:

carboxylate ester (—(CO)—O—);

enol ether (—CH═CH—O—);

acetal (—O—CR₂—O—);

hemiacetal (—CH(OH)—O—);

anhydride (—(CO)—O—(CO)—);

carbonate (—O—(CO)—O);

N-substituted amide (—(CO)—NR—);

N-substituted urethane (—O—(CO)—NR—);

N-substituted imino (—CH₂—NR—, —CHR—NR—, (—CR₂—NR—,);

imido (—CH═N—);

substituted imido (—CR═N—);

lactam (-Cy¹(=O)- where Cy¹ is a three- to seven, typically a five- orsix-membered nitrogen containing heterocycle, e.g., pyrrolidone);

cyclic imido (-Cy²- where Cy² is a five- or six-membered ring containinga —CH═N— linkage);

substituted cyclic imido (substituted -Cy²- where Cy² is a five- orsix-membered ring containing a —CR═N— linkage);

N,N-disubstituted hydrazo (—NR—NR—);

bicyclic acetal (-Cy³Cy⁴- wherein Cy³ and Cy⁴ are five- or six-memberedrings each containing an acetal linkage);

thioester (—(CO)—S—);

phosphonic ester (—P(O)(OR)—O—);

sulfonic ester (—SO₂—OR—);

ortho ester (—C(OR)₂—O—);

ether (—O—), including cyclic ether;

thio (—S—);

dithio (—S—S—); and

siloxyl (—SiR′R″—O—SiR′R″— or —O—SiR′R″—O—); and

silazyl (—SiR′R″—NR—SiR′R″— or —NR—SiR′R″—NR—).

In the above structures, R is hydrocarbyl (e.g., C₁-C₂₄ alkyl, C₅-C₂₄aryl, C₆-C₂₄ alkaryl, or C₆-C₂₄ aralkyl, preferably C₁-C₁₂ alkyl, C₅-C₁₄aryl, C₆-C₁₆₄ alkaryl, or C₆-C₁₆ aralkyl, more preferably C₁-C₆ alkyl),substituted hydrocarbyl (e.g., substituted C₁-C₂₄ alkyl, C₅-C₂₄ aryl,C₆-C₂₄ alkaryl, or C₆-C₂₄ aralkyl, preferably substituted C₁-C₁₂ alkyl,C₅-C₁₄ aryl, C₆-C₁₆ alkaryl, or C₆-C₁₆ aralkyl, more preferablysubstituted C₁-C₆ alkyl), heteroatom-containing hydrocarbyl (e.g.,C₁-C₂₄ heteroalkyl, C₅-C₂₄ heteroaryl, C₆-C₂₄ heteroalkaryl, or C₆-C₂₄heteroaralkyl, preferably C₁-C₁₂ heteroalkyl, C₅-C₁₄ heteroaryl, C₆-C₁₆heteroalkaryl, or C₆-C₁₆ heteroaralkyl, more preferably C₁-C₆heteroalkyl), or s(e.g., substituted C₁-C₂₄ heteroalkyl, C₅-C₂₄heteroaryl, C₆-C₂₄ heteroalkaryl, or C₆-C₂₄ heteroaralkyl, preferablysubstituted C₁-C₁₂ heteroalkyl, C₅-C₁₄ heteroaryl, C₆-C₁₆ heteroalkaryl,or C₆-C₁₆ heteroaralkyl, more preferably substituted C₁-C₆ heteroalkyl).Optimally, R is lower alkyl. In the siloxyl and silazyl linkages, R′ andR″ are independently selected from hydrido, hydrocarbyl as definedabove, and alkoxy, and are preferably hydrido, lower alkyl, or loweralkoxy.

Exemplary hydrolyzable monomers thus include, but are not limited to:

esters having the structure

enol ethers having the structure

acetals having the structure

hemiacetals having the structure

anhydrides having the structure

cyclic diketals having the structure

siloxanes having the structure

imides having the structure

wherein R³, R⁴, L¹, L², m and n are as defined previously, and R⁵ and R⁶are independently hydrido or alkyl, preferably hydrido or lower alkyl,most preferably hydrido.

As noted previously, L¹ and L² can also contain a hydrolyticallycleavable linkage. A representative monomer in which this is the case isthe diester having the structure

It will be appreciated that this compound corresponds to a monomer ofstructure R³CH═CH-(L¹)_(m)-X-(L²)_(n)-CH═CHR⁴ in which m is 0, X is—(CO)—O—, n is 1, and L² is —CH₂—O—(CO)—).

The copolymers are formed by polymerization, catalyzed by a solubletransition metal catalyst, as described further below. The molecularweight of the copolymer is sufficient to provide the physical propertiesrequired for the final use of the copolymer, e.g., in packaging,disposable containers, disposable diapers, etc. For example, themolecular weight (weight average) of a polyethylene copolymer willgenerally be in the range of about 20,000 to about 300,000 or greater(preferably in the range of about 60,000 to 300,000), an approximateuseful range for commercial linear polyethylenes.

The hydrolyzable component of the copolymer is found within the secondmonomer unit, —CHR³—CH₂-(L¹)_(m)-X-(L²)_(n)-CH₂—CHR⁴—, incorporatedwithin the backbone of the copolymer wherein R³, R⁴, L¹, L², m and n areas defined above. Accordingly, the copolymer is degraded at the linkageX under aqueous conditions, generally involving acidic or basichydrolysis, thus breaking a copolymer into lower molecular weightsegments. Depending on the nature of X, these lower molecular weightsegments typically have polar end groups, thus increasing the watersolubility, or dispersability, of the fragments.

To increase the effectiveness of the hydrolyzable comonomer indegradation of the copolymer, the copolymer has no adjacent hydrolyzablemonomer units and none would be expected to occur in the polymerizationsdescribed herein. It will be appreciated that copolymers having a higherratio of hydrolyzable comonomer to olefinic monomer will undergo agreater reduction in average molecular weight on degradation. Higherlevels of hydrolyzable comonomer will also generally have a greatereffect on the physical properties, such as the hydrophobicity, of thecopolymer, and are expected to reduce degree of polymerization (i.e.,molecular weight) as well. Therefore, the desired fraction ofhydrolyzable comonomer units in the copolymer will depend on the finaluse, and desired extent of degradability, of the copolymer. Asignificant advantage of the invention, however, is that a far greaterproportion of the hydrolyzable monomer in the monomer mixture undergoingpolymerization can now be incorporated into the resulting copolymer.That is, on the order of 50 mole % to 100 mole %, preferably about 60mole % to 100 mole %, and most preferably about 70 mole % to 100 mole %of the total hydrolyzable monomer in the feed is actually incorporatedinto the copolymer.

As a general matter, the method of the invention enables the preparationof copolymers containing at least 10 mole %, or at least 15 mole %, orat least 20 mole %, or at least 25 mole %, hydrolyzable monomer units,and up to 50 mole % or more. For most applications, however, thecopolymer will contain about 0.1 mole % to about 50 mole % hydrolyzablemonomer units (corresponding to a 99.9:1 to 1:1 mole ratio ofnonhydrolyzable monomer units to hydrolyzable monomer units).

III. Polymerization

The copolymers are prepared by transition metal-catalyzedpolymerization, a preferred method for forming olefin copolymers withgood control of molecular weight, molecular weight distribution, andstereoregularity. Procedures for such polymerizations are well known inthe art.

In general, the present polymers are prepared using soluble transitionmetal catalysts. Such catalysts include metallocenes, preferably thosederived from Group 4, 5, and 6 transition metals, typically Ti, Hf, orZr, although complexes of V, Nb and Mo are also employed. Thesecomplexes include at least one ligand derived from a cyclopentadienering, or a multiring system containing a cyclopentadiene ring, such asfluorene or indene. The ring or ring system may be substituted withalkyl, aryl, or other groups not containing active hydrogen, such asethers, tertiary amines, tertiary boranes, tertiary silanes, or halides.Other ligands on the transition metal are typically halides, lower alkylgroups, or tertiary amines, but may also be selected from a wide varietyof other groups, such as aryl, alkoxy, acetoacetate, carbonyl, nitrile,isonitrile, tertiary amine or phosphine, π-allyl, or cyclic unsaturatedhydrocarbons such as cycloheptatriene. Two of the ligands may bebridged, e.g., by a chain containing linkages selected from alkyl andalkylsilane, to formed constrained-geometry catalysts. Examples ofmetallocene catalysts include cyclopentadienyl titanium trichloride,bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)dimethylzirconium, (pentamethylcyclopentadienyl)titanium trimethoxide,bis-2-(3,5-di(trifluoromethyl)phenyl)-indenyl hafnium dichloride,(3,5-di(trifluoromethyl)phenyl)indenyl hafnium trichloride, and bridgedcompounds such as dimethylsilylbis(cyclopentadienyl)hafnium dichloride,dimethylsilylbis(2-methyl-4-phenyl indenyl)zirconium dichloride, and(tert-burylamido)dimethyl (cyclopentadienyl)silane zirconium dichloride.Other suitable metallocene catalysts include those described in U.S.Pat. Nos. 6,048,992 and 6,369,253 to Wilson Jr. et al., both of whichare assigned to SRI International (Menlo Park, Calif.).

Also useful are Brookhart-type catalysts, based on 1,2-diimine complexesof Group 8 transition metals, particularly Ni, Pd, Fe, and Co; Cu, Ag,and Au complexes have also been described. These catalysts are typicallytransition metal complexes having the structure

wherein M is generally selected from Pd(II), Fe(II), Co(II), and Ni(II),X¹ and X² are heteroatoms, generally N, R^(A) and R^(B) are hydrocarbyl,optionally substituted and/or heteroatom-containing, Q¹ is ahydrocarbylene linkage, optionally substituted and/orheteroatom-containing, Q² and Q³ are each a univalent radical such ashydride, halide, lower alkyl, or lower alkoxy. Often, one or more cyclicgroups are present, for example, when R^(A) and/or R^(B) are linked toan atom contained within the linkage Q¹ (to form an N-heterocycle whenX¹ and/or X² are N), or when two or more substituents on adjacent atomswithin Q¹ are linked. See, for example, Johnson et al. (1995), supra,Johnson et al. (1996) J. Am. Chem. Soc. 118:267-8, and Killian et al.(19979) Organometallics 16:2005-7. Related cobalt- and iron-basedcatalysts employ tridentate imine ligands (Small et al. (1998) J. Am.Chem. Soc. 120:4049-50). Other complexes may be used havingimine-containing ligands other than diimines, or analogouspyridyl-containing or bipyridyl ligands. Other suitable Brookhart-typecatalysts and analogs thereof are described in U.S. Pat. No. 6,355,746to Tagge et al.

In carrying out the present polymerization reaction, the transitionmetal complexes described herein as polymerization catalysts arepreferably, although not necessarily, used in conjunction with acatalyst activator that converts the electronically neutral metal centerof the complex to a cation, such that the complex is rendered cationicor zwitterionic. Thus, it is preferred that prior to or uponpolymerization, the transition metal complex selected as thepolymerization catalyst is incorporated into a catalyst system thatincludes such an activator. Suitable catalyst activators are those thatare typically referred to as ionic cocatalysts; such compounds include,for example, include metal alkyls, hydrides, alkylhydrides, andalkylhalides, such as alkyllithium compounds, dialkylzinc compounds,trialkyl boron compounds, trialkylaluminum compounds, alkylaluminumhalides and hydrides, and tetraalkylgermanium compounds. Specificexamples of useful activators include n-butyllithium, diethylzinc,di-n-propylzinc, triethylboron, triethylaluminum, triisobutylaluminum,tri-n-hexylaluminum, ethylaluminum dichloride, dibromide and dihydride,isobutyl aluminum dichloride, dibromide and dihydride,di-n-propylaluminum chloride, bromide and hydride, diisobutyl-aluminumchloride, bromide and hydride, ethylaluminum sesquichloride, methylaluminoxane (“MAO”), hexaisobutyl aluminoxane, tetraisobutylaluminoxane, polymethyl aluminoxane, tri-n-octylaluminum, tetramethylgermanium, and the like. Other activators that are typically referred toas ionic cocatalysts may also be used; such compounds include, forexample, (C₆H₆)₃ ⁺, C₆H₅—NH₂CH₃ ⁺, and fluorohydrocarbylboron compoundssuch as tetra(pentafluorophenyl)borate, sodiumtetrakis[(bis-3,5-trifluoromethyl)phenyl]borate, H⁺(OCH₂CH₃)₂[(bis-3,5-trifluoromethyl)-phenyl]borate,trityltetra(pentafluorophenyl)borate, and trifluoromethanesulfonate, andsalts or acids of BF₄ ⁻, Ph₄B⁻ (Ph=phenyl), p-toluenesulfonate, SbF₆ ⁻,and PF₆ ⁻. Mixtures of activators may, if desired, be used.

The catalysts are used to prepare polymeric compositions usingconventional polymerization techniques known to those skilled in the artand/or described in the pertinent literature. The monomer(s), catalystand catalyst activator are contacted at a suitable temperature atreduced, elevated or atmospheric pressure, under an inert atmosphere,for a time effective to produce the desired polymer composition. Thecatalyst may be used as is or supported on a suitable support. In oneembodiment, the catalysts are used as homogeneous catalysts, i.e., asunsupported catalysts, in a gas phase or liquid phase polymerizationprocess. A solvent may, if desired, be employed. The reaction may beconducted under solution or slurry conditions, in a suspension using aperfluorinated hydrocarbon or similar liquid, in the gas phase, or in asolid phase powder polymerization. Various additives may be incorporatedinto the mixture; particularly preferred additives are neutral Lewisbases such as amines, anilines and the like, which can accelerate therate of polymerization.

Liquid phase polymerization generally involves contacting the monomer ormonomers with the catalyst/activator mixture in a polymerizationdiluent, and allowing reaction to occur under polymerization conditions,i.e., for a time and at a temperature sufficient to produce the desiredpolymer product. The polymerization diluents are generally inertsubstances for example, aliphatic or aromatic hydrocarbons, e.g.,liquified ethane, propane, butane, isobutane, n-butane, n-hexane,isooctane, cyclohexane, methylcyclohexane, cyclopentane,methylcyclopentane, cycloheptane, methylcycloheptane, benzene,ethylbenzene, toluene, xylene, kerosene, Isopar® M, Isopar® E, andmixtures thereof. Liquid olefins or the like which serve as the monomersor comonomers in the polymerization process may also serve as thediluent; such olefins include, for example, ethylene, propylene, butene,1-hexene and the like.

The amount of catalyst in the diluent will generally be in the range ofabout 0.01 to 1.0 mmoles/liter, with activator added such that the ratioof catalyst to activator is in the range of from about 10:1 to 1:2000,preferably in the range of from about 1:1 to about 1:1200, on a molarbasis.

Polymerization may be conducted under an inert atmosphere such asnitrogen, argon, or the like, or may be conducted under vacuum.Preferably, polymerization is conducted in an atmosphere wherein thepartial pressure of reacting monomer is maximized. Liquid phasepolymerization may be carried out at reduced, elevated or atmosphericpressures. In the absence of added solvent, i.e., when the olefinicmonomer serves as the diluent, elevated pressures are preferred.Typically, high pressure polymerization in the absence of solvent iscarried out at temperatures in the range of about 180° C. to about 300°C., preferably in the range of about 250° C. to about 270° C., and atpressures on the order of 200 to 20,000 atm, typically in the range ofabout 1000 to 3000 atm. When solvent is added, polymerization isgenerally conducted at temperatures in the range of about 150° C. toabout 300° C., preferably in the range of about 220° C. to about 250°C., and at pressures on the order of 10 to 2000 atm.

Polymerization may also take place in the gas phase, e.g., in afluidized or stirred bed reactor, using temperatures in the range ofapproximately 60° C. to 120° C. and pressures in the range ofapproximately 10 to 1000 atm.

In gas and slurry phase polymerizations, the catalyst is used in aheterogeneous process, i.e., supported on an inert inorganic substrate.Conventional materials can be used for the support, and are typicallyparticulate, porous materials; examples include oxides of silicon andaluminum, or halides of magnesium and aluminum. Particularly preferredsupports from a commercial standpoint are silicon dioxide and magnesiumdichloride.

The polymeric product resulting from the aforementioned reaction may berecovered by filtration or other suitable techniques. If desired,additives and adjuvants may be incorporated into the polymer compositionprior to, during, or following polymerization; such compounds include,for example, pigments, antioxidants, lubricants and plasticizers.

According to generally accepted mechanisms of addition polymerizationusing transition metal catalysts, incorporation of a monomer having abulky substituent on the double bond, as in the hydrolyzable comonomersdescribed herein, reduces the rate of further propagation. Thus, thereactive intermediate, having incorporated the hydrolyzable comonomer,is more likely to next undergo a chain transfer or terminating step thanto continue propagation. For this reason, contiguous blocks of thehydrolyzable comonomer are not expected to be produced. In addition, itis expected that the hydrolyzable monomers are incorporated as chainextending components (that is, contained within the linear backbone ofthe polymer), rather than as crosslinking components. The latterstructure would result from further propagation after addition of thediene monomer, which is not expected to be favorable. However, becausethis feature of metallocene catalysis varies among individual catalysts,some degree of crosslinking could be incorporated, if desired, by theuse of a catalyst less sensitive to bulky substituents.

Various additives can optionally be used in preparing copolymercompositions according to the present invention, or added afterpolymerization has been completed. These additives may be included tomodifying the stability, color, strength, or other properties of theresultant polymeric compositions. Suitable additives include suchantioxidants as Hindered Amine Light Stabilizers (HALS) (e.g.,bis-(1,2,2,5,5-pentamethylpiperidinyl)sebacate (Tinuvin 765)), phenolicantioxidants (e.g., t-butylcatechol), triethyl phosphite,t-butylhydroxyquinone and the like. In some cases, inclusion of suchantioxidants can promote biodegradability of the polymers. Suchadditives may prevent premature autooxidation of the unsaturated polymerchains that are necessary for accelerated biodegradation.

Other optional additives may be included to enhance the degradability ofthe compositions upon exposure to light, particularly ultraviolet lightin sunlight. Such additives, generally referred to as photosensitizers,are well known in the art, and include, by way of example, benzophenone,anthrone, anthraquinone, xanthone, 3-ketosteroids; andhydroxy-substituted 2,4-pentadienophenones. See, for example, U.S. Pat.No. 3,888,804 to Swanholm et al.

Other optional additives that may be included are compounds that canpromote the oxidation of the copolymer, thus enhancing itsdegradability. Such prooxidants may be the transition metal salts oforganic acids, e.g., stearates, naphthenates, oleates, and the like. SeeU.S. Pat. No. 4,983,651 to Griffin; U.S. Pat. No. 3,592,792 to Newlandet al.; U.S. Pat. No. 3,454,510 to Greer et al.; U.S. Pat. No. 5,096,941to Harnden; U.S. Pat. No. 3,951,884 to Miyoshi, et al.; and U.S. Pat.No. 3,956,424 to Iizuka et al.

Other additives that can be included in the degradable compositions areplasticizers, slip agents, antistatic agents, release agents,tackifiers, dyes, pigments, flame retardants, fillers such as carbonblack, calcium carbonate, silicates, opacifiers such as titaniumdioxide, and other additives well known to those skilled in the art.Examples of plasticizers are dioctyl azelate, dioctyl sebacate, ordioctyl adipate and other long chain length alkyl esters of di-, tri-,and tetra-carboxylic acids such as azelaic, sebacic, adipic, phthalic,terephthalic, isophthalic, and the like. Effective amounts of suchplasticizers are typically in the range of from about 5 wt. % to 30 wt.% of the copolymer, more typically from about 7 wt. % to about 15 wt. %of the copolymer. Examples of slip agents are those commonly derivedfrom amides of fatty acids having about 12 to 22 carbon atoms. Suchagents can augment the anti-blocking properties of films and may beincorporated in amounts of from about 0.05% to about 3% based on the dryweight of the films when used. Examples of antistatic agents includeethoxylated amines and quaternary amine salts having organicconstituents of about 12-18 carbon atoms in length. Agents of this typemay slowly diffuse to the surface of the polymer and, because of theirionic character, form an electrically conductive layer on the surface.Antistatic agents may be incorporated in amounts of from about 1% toabout 5% based on the dry weight of the films when used.

IV. Degradable Products

The hydrolyzable copolymers useful in the present invention can becombined with other degradable components by mixing, laminating,blending, coextrusion, etc., to provide degradable polymer-containingcompositions that can be subsequently formed into degradable articles.These degradable polymer-containing compositions comprise from about 20to about 99 wt. % copolymer as previously described and from about 1 wt.% to about 80 wt. % of another degradable component. Typically, thesedegradable copolymer-containing compositions comprise from about 30 wt.% to about 95 wt. % copolymer and from about 5 wt. % to about 70 wt. %the other degradable component, more typically from about 50 wt. % toabout 90 wt. % copolymer and from about 10 wt. % to about 50 wt. % theother degradable component. The precise amounts of the copolymer andother degradable component(s) present in the degradablecopolymer-containing composition will depend upon a number of factors,including the particular article to be made from the composition and itsintended use. The other degradable component(s) may be hydrolyzable,cleavable with light, enzymatically degradable, or degradable via someother mechanism.

Other degradable components that may be suitable for use in the presentinvention include other degradable polymers such as lactic acid polymersand copolymers (e.g., poly(lactic acid) and poly(lactide-co-glycolide)),poly(hydroxy alkanoates) such as the homopolymers of 3-hydroxybutyrateand 4-hydroxybutyrate, and the copolymers of hydroxybutyrate with otherhydroxy acids, for example, 3-hydroxypropionate, 3-hydroxyvalerate,3-hydroxyhexanoate, 3-hydroxyoctanoate, or longer chain hydroxy acids(e.g., C₉-C₁₂ hydroxy acids), starch, natural rubber, gutta percha,balata, dextran, chitin, cellulose, wood flour, derivatives ofbiodegradable polymers including cellulose esters such as chitosan,cellulose nitrate, cellulose acetate, and block copolymers ofpolycaprolactone with polydienes; and the like. See U.S. Pat. No.5,216,043 to Sipinen et al. and U.S. Pat. No.3,921,333 to Clendinning etal. Particularly preferred additional degradable components includedextran, cis-polyisoprene and starch.

Suitable starches include any unmodified starch from cereal grains orroot crops such as corn (e.g., zein), wheat, rice, potato, and tapioca.The amylose and amylopectin components of starch as well as modifiedstarch products such as partially depolymerized starches and derivatizedstarches can also be used. The term “starch” encompasses all suchstarches, including starch components, modified starch products, andstarch degradation products. The terms “modified starch” and “starchdegradation products” include for example pregelatinized starches (coldswelling starch), acid modified starches, oxidized starches, slightlycrosslinked starches, starch ethers, starch esters, dialdehyde starches,and degradation products of starch hydrolyzed products and dexatrenes.The particle size of the starch granules can, however, limit some of theattainable physical dimensions of certain articles, such as the gauge ofthin films and coatings and the diameter of fibers. To facilitate thepreparation of thinner films and fibers, the particle size of starchescan be decreased by grinding with oversized particles being removed byprocedures such as air classification. In addition, starch granules canbe modified by treatments such as pregelatinization in whichconcentrated starch/water slurries are dried quickly by drum drying,spray drying, foam heat or puff extrusion. The pregelatinized starch canbe dried and optionally ground and classified to yield fine starchparticles. Other degradable derivatives of starch can be treatedsimilarly. If desired, a mixture of two or more starches can be used.

In the preparation of degradable films, it is preferred that the starchbe gelatinized. Gelatinization can be achieved by any known proceduresuch as heating in the presence of water or an aqueous solution attemperatures above about 60° C., until the starch granules aresufficiently swollen and disrupted that they form a smooth viscousdispersion in the water. The gelatinization can be carried out eitherbefore or after admixing the starch with the copolymer.

In preparing the copolymer-containing compositions, the starch (e.g.,starch granules) is normally mixed or otherwise blended with the rawcopolymer during processing to provide a composition suitable forcasting, extruding, molding, or other fabrication procedure. If thecopolymerization will efficiently take place under conditions such thatthe starch is not altered chemically or physically, starch granules canalso be added to the copolymerization mixture prior to polymerization.

The hydrolyzable copolymers of the invention may, in addition, or in thealternatively, be blended with nondegradable polymers prior tofabrication of degradable articles. By “nondegradable” is meant that apolymer is not degradable hydrolytically, enzymatically, or undertypical conditions of waste disposal involving exposure to theenvironment. The nondegradable polymers may be selected to provide thedegradable with enhanced tensile strength, thermal stability,flexibility, or other properties that may be desirable for a particulartype of degradable article. Such polymers include low densitypolyethylene (LDPE), high density polyethylene (HDPE), linear lowdensity polyethylene (LLDPE), ethylene-propylene rubber, polystyrene,polyvinylchloride (PVC), polyhalocarbons, and copolymers of ethylenewith propylene, isobutene, butene, hexene, octene, vinyl chloride, vinylalcohol, and the like. The polymer blends can also include rubbermaterials such as polychloroprene, polybutadiene, polyisoprene,polyisobutylene, nitrile-butadiene rubber, styrene-butadiene rubber,chlorinated polyethylene, chlorosulfonated polyethylene, epichlorohydrinrubber, butyl rubber, or halobutyl rubber.

Typically, if a nondegradable polymer is blended with one or moredegradable copolymers of the invention and optionally other degradablepolymers, the degradable portion of the composition will generallyrepresent 5 wt. % to about 99 wt. % of the composition, preferably about10 wt. % to 95 wt. % of the composition, most typically about 15 wt. %to about 90 wt. % of the composition.

The invention enables the preparation of a wide variety of products,e.g., films, fibers, foams, woven fabrics, nonwoven fabrics, and moldedarticles, for which degradability is desired. For example, the presentcopolymers can be used to make shaped articles by injection molding,blow molding, thermal forming of sheets, rotational molding of powder,extrusion, and other molding or shaping processes. The following is anonexclusive list of such end uses and articles: agricultural filmproducts, including agricultural mulch and film products containingseeds, fertilizers, pesticides, herbicides, and the like; adhesive tapesubstrates; bed linens, including sheets and pillowcases; containers,including bottles and cartons; disposable absorbent articles, such asdiapers, sanitary napkins, incontinence pads, pantyliners, and tampons;packaging materials; bags, e.g., shopping bags, dust bags, garment bags,garbage bags, lawn waste bags, and industrial bags; labels; tags;protective clothing; surgical drapes; sponges; tampon applicators;disposable syringes; temporary enclosures and temporary siding; toys;wipes; foamed plastic products such as food packaging, foamed packingcomponents, bottles or containers prepared by injection molding orvacuum forming; and controlled release pellets, strips, and tabscontaining an active ingredient intended for slow release, includingcontrolled release pharmaceutical products, products containingpesticides, and products containing pest-repellents such as flea collarsor cattle ear tags.

Films, fibers, foams, woven fabrics, and nonwoven fabrics prepared fromthe copolymers of the invention have particular utility in disposableabsorbent articles. By “absorbent article” herein is meant a consumerproduct that is capable of absorbing significant quantities of blood,urine or other fluids, like aqueous fecal matter (runny bowelmovements), discharged by an incontinent wearer. Examples of suchabsorbent articles include disposable diapers, incontinence garments andpads, personal hygiene materials such as diapers, sanitary napkins,incontinence pads, pantyliners, disposable training pants, bed pads,clothing shields, and the like.

Absorbent articles such as diapers, sanitary napkins, incontinence pads,pantyliners, and training pants typically contain an absorbent corebetween a fluid-impermeable backsheet and a fluid-permeable topsheet,wherein when the article is in use, it is positioned so that fluid comesinto contact with the topsheet and flows therethrough to the absorbentcore, which serves to absorb the fluid and contain it by virtue of thebacksheet. At least one of the topsheet and backsheet and preferablyboth are made from the copolymers of the present invention, or blends ofthese copolymers with other degradable or nondegradable components asexplained above. The topsheet is usually positioned adjacent to the bodysurface of the absorbent core. The topsheet is preferably joined to thebacksheet by attachment means such as those well known in the art. Inpreferred absorbent articles, the topsheet and the backsheet are joineddirectly to each other at the periphery thereof. See U.S. Pat. No.3,860,003 to Buell; U.S. Pat. No. 4,808,178 to Aziz et al.; U.S. Pat.No. 4,695,278 to Lawson; and U.S. Pat. No. 4,816,025 to Foreman, forrepresentative diaper configurations.

The backsheet prevents body fluids that are absorbed and contained inthe absorbent core from wetting articles that are in contact with theabsorbent article such as pants, pajamas, undergarments, and the like.The backsheet can be in the form of a woven or nonwoven material, afilm, or a composite material such as a film-coated nonwoven material.Preferably, the backsheet is a nonwoven material having a thickness offrom about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils). Thebacksheet is preferably embossed and/or matte finished to provide a moreclothlike appearance. Further, the backsheet can be modified to permitvapors to escape from the absorbent core (i.e., be breathable) whilestill preventing body fluids from passing through the backsheet. In apreferred embodiment, the present copolymers are simply cast intononperforated, flexible sheets of a woven or nonwoven material.

The topsheet is preferably compliant, soft feeling, and non-irritatingto the wearer's skin. Further, the topsheet is fluid permeable andpreferably non-absorbent, thereby allowing body fluids to penetratethrough the entirety of the topsheet to the absorbent core. Thus, thesurface of the formed film that is in contact with the body remains dry,thereby reducing body soiling and creating a more comfortable feel forthe wearer. A suitable topsheet can be manufactured in a wide variety offorms such as nonwoven fabrics; apertured formed films, hydroformedfilms; porous foams; reticulated films; and scrims. Preferred topsheetsfor use in absorbent articles of the present invention are selected fromnonwoven topsheets and apertured formed film topsheets. In thefabrication of nonwoven (and woven) topsheet materials, the presentcopolymers can be provided in the form of filaments from which anonwoven (or woven) web is made. With apertured formed film topsheets,the copolymers can be cast as sheets having a multiplicity ofperforations therethrough. The formation of perforated sheets and websfor use as topsheets is well known in the art. Suitable methods formaking formed films are described in U.S. Pat. No. 3,929,135 toThompson; U.S. Pat. No. 4,324,246 to Mullane, et al.; U.S. Pat. No.4,342,314 to Radel et al.; U.S. Pat. No. 4,463,045 to Ahr et al.; andU.S. Pat. No. 5,006,394 to Baird. Each of these patents are incorporatedherein by reference. Microapertured formed film topsheets and especiallymethods for making such topsheets are disclosed in U.S. Pat. No.4,609,518 to Curro et al., and U.S. Pat. No. 4,629,643 to Curro et al.,which are incorporated by reference.

The body surface of the formed film topsheet can be hydrophilic so as tohelp body fluids to transfer through the topsheet faster than if thebody surface was not hydrophilic so as to diminish the likelihood thatfluid will flow off the topsheet rather than flowing into and beingabsorbed by the absorbent structure. In one embodiment, surfactant isincorporated into the polymer of the formed film topsheet. In anotherembodiment, the body surface of the topsheet can be made hydrophilic bytreating it with a surfactant such as is described in U.S. Pat. No.4,950,264 to Osborn, which is incorporated herein by reference.

The absorbent core can be composed of any number of typical absorbentmaterials used in diapers, sanitary napkins, incontinence pads, and thelike. The absorbent material is generally cellulosic, e.g., composed ofoxidized cellulose or ordinary cellulose fibers, optionally containingadditional absorbent materials such as acrylates, starch-graftedacrylates, and various gums and/or saccharidic gelling materials thatabsorb and hold on the order of ten to fifty times their weight ofwater. Such materials are thoroughly described in the patent literaturerelating to disposable sanitary products, and are available from variouscommercial sources. For disposable diapers, the entire article may befabricated from the aforementioned materials, i.e., having an outerbacksheet, an inner topsheet, and an absorbent core therebetween. Thediaper may be a single integral structure that, once fitted onto aninfant, is secured by a fastener on either side of the waist, e.g., tapeor other adhesive means. The diaper may also be in the form of anundergarment with two leg holes, in which case it is preferred that anelastic material be incorporated as a leg band to ensure a snug fit ofthe diaper around the legs. Incontinence pads are also structured inthis manner.

The degradable copolymers of the invention are also useful for beveragecarriers comprising a plurality of connected annular sections where eachannular section is capable of releasably securing a container such as abottle or can. Such carriers may be referred to as “six-pack rings,”although the carrier can typically comprise from two to twelve suchannular rings, more typically from four to six rings. See, for example,U.S. Pat. No. RE 29,873 to Cunningham, and U.S. Pat. No. 3,938,656 toOwen, which disclose “six-pack rings” of various types.

Another use of the degradable copolymers is in the fabrication oftemporary coverings for the ground and are especially useful asagricultural mulch. Ground coverings may be provided in the form offilms or sheets that can be spread out or otherwise applied to theground to be covered. Ground coverings that are made from blends of thepresent copolymers with starch can be particularly desirable since thestarch portion of the covering may be able to disintegrate relativelyquickly with the residual copolymer ultimately degrading completely.

The degradable copolymers can also be used in degradable packagingmaterials for wrapping various products. Edible products such as foodsand beverages may be packaged with such materials. Packaging materialsmade from blends of the copolymers with starch can be particularlydesirable since such materials can disintegrate fairly rapidly ifimproperly discarded as litter and are expected to ultimately degradecompletely.

The copolymers can also be used to deliver pesticides, insectrepellents, herbicides, and the like. For example, when blended withsuitable pesticides and shaped into a strip, the copolymers can formdegradable flea or tick collars. Similar blends formed into tags with asuitable attachment device can form degradable ear tags used forlivestock to ward off flies and other insects. Suitable pesticides mayinclude various chlorinated types such as Chlordane,pyrethroid/pyrethrin types such as Permethrin, organophosphates andcarbamates such as Malathion, carbaryl and diazinon, repellents such asm-diethyl toluamide, diethylphenyl acetamide, and limonene, insectgrowth regulants such as methoprene, hydroprene, and fenvalerate,synergists such as piperonyl butoxide, and the like.

The copolymers are also suitable for use as fibers or filaments innonwoven materials. Fibers and filaments are interchangeable terms inthe general sense, but where a more specific acknowledgment of length isappropriate, the term “fibers” is intended to refer to short filamentsas in “staple fibers.” The degradable copolymers can be converted tofibers or filaments by meltspinning techniques or the like. Deniers offrom about 2 to about 15 dpf are most common. The filaments can be usedas they are spun (undrawn) or they may be used in a stretched (drawn ororiented) condition. Drawing to reduce denier or for increasingorientation can be accomplished by the usual procedures known in theart.

Suitable thermoplastic fibers according to the present invention can bein the form of thermally bondable bicomponent fibers. As used herein,“biocomponent fibers” refers to thermoplastic fibers that comprise acore fiber made from one polymer (or copolymer) that is encased within athermoplastic sheath made from a different polymer (or copolymer). Thepolymer comprising the sheath often melts at a different, typicallylower, temperature than the polymer comprising the core. As a result,these bicomponent fibers can provide thermal bonding by controlledmelting of the sheath polymer, while retaining the desirable strengthcharacteristics of the core polymer. An example of a degradablebicomponent fiber according to the present invention is a sheath made ofthe copolymer surrounding a core made from a higher melting degradablepolymer such as a polyvinyl alcohol or rayon or a copolymer with similarproperties.

Bicomponent fibers according to the invention can be concentric oreccentric. As used herein, the terms “concentric” and “eccentric” referto whether the sheath has a thickness that is even, or uneven, throughthe cross-sectional area of the bicomponent fiber. Eccentric bicomponentfibers can be desirable in providing more compressive strength at lowerfiber thicknesses. Suitable bicomponent fibers for use herein can beeither uncrimped (i.e., unbent) or crimped (i.e., bent). Bicomponentfibers can be crimped by typical textile means such as, for example, astuffer box method or the gear crimp method to achieve a predominantlytwo-dimensional or “flat” crimp.

Fibers made from the degradable copolymers of the present invention canbe formed into nonwoven fabrics by a number of processes to providespunbonded fabrics and fabrics made using staple fibers. Spunbondednonwovens can be prepared by spinning and laying down simultaneouslyinto webs of continuous filaments using known methods of distributingthe threadline in the desired orientation in the web plane. Such webscan be thermally bonded under suitable conditions of time, temperatureand pressure to yield strong fabrics with tensile properties that areusually superior to those obtained with staple webs. Bonding can also becarried out by using suitable adhesives and both these methods can beused to make point bonded or area bonded fabrics. Needle punching canalso be used to give the webs stability and strength. Spunbonded fabricscan also be made by melt blowing these polymers. In this process, astream of the molten polymer or blend is extruded into a high velocitystream of heated dry air and a bonded web formed directly on a screenconveyor from the resultant fibers. Nonwoven fabrics can also be made bydirect extrusion through a rotating die into a netlike product. See U.S.Pat. No. 5,219,646 to Gallagher et al., which is incorporated herein byreference.

The degradable copolymers can also be used to make degradable foamedplastics. These include foamed containers, foamed packing components(e.g., “peanuts”), and the like. The foamed plastic can be made bycompounding the copolymer or blend with a suitable blowing agent such aspentane and then heating to volatilize the blowing agent. Typically, asurfactant suitable for stabilizing the air-liquid interface is employedas well. The foam can be used as is or can be cut into smaller pieces(commonly referred to as “peanuts”) suitable as loose packaging filler.

Films of the degradable copolymers or blends can be laminated to varioussheets and films using procedures well known in the art to providesheets and films having desired properties. The choice of laminate andfilm may be varied for a particular purpose.

Any of the aforementioned products may be prepared from the degradablecopolymers per se, with a polymer blend composed of at least onedegradable copolymer of the invention and at least one other degradablecomponent and/or nondegradable copolymer, or from a degradablecomposition containing a degradable copolymer of the invention per se, apolymer blend composed of at least one degradable copolymer of theinvention and at least one other degradable component and/ornondegradable copolymer, and one or more additives as described earlierherein, e.g., prooxidants, stability enhancers, tensile strengthenhancers, photosensitizers, colorants, plasticizers, tackifiers, andfillers.

The invention additionally pertains to degradable articles, includingfilms, fibers, foams, woven fabrics, nonwoven fabrics, and moldedarticles fabricated from olefin polymers containing substantially inertmonomer units (e.g., monomer units resulting from polymerization ofolefins not containing any heteroatoms or non-hydrocarbyl substituents)and cleavable monomer units, i.e., monomer units containing a site thatis chemically, enzymatically, or photolytically cleavable, preferablyhydrolytically cleavable, wherein the cleavable monomer units representat least 10 mole %, or at least 15 mole %, or at least 20 mole % of thecopolymer, and up to 50 mole % or more. For most applications, as withthe degradable copolymers of the invention, the copolymer will containabout 0.1 mole % to about 50 mole % of the cleavable monomer units.

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiments thereof, that thedescription above as well as the examples which follow are intended toillustrate and not limit the scope of the invention. Other aspects,advantages and modifications within the scope of the invention will beapparent to those skilled in the art to which the invention pertains.

All patents, patent applications, journal articles and other referencecited herein are incorporated by reference in their entireties.

Experimental

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how toprepare and use the catalysts of the invention. Efforts have been madeto ensure accuracy with respect to numbers (e.g., amounts, temperature,etc.) but some errors and deviations should be accounted for. Unlessindicated otherwise, parts are parts by weight, temperature is in ° C.and pressure is at or near atmospheric.

Examples 1 and 2 describe the copolymerization of a diolefin containinga bicyclic acetal linkage with ethylene, and Examples 3 and 4 describecopolymerization of ethylene with olefins containing a siloxane linkage.The amount of comonomer used in each example, based on the estimatedinitial amount of ethylene in the pressurized reactor, was as follows:Examples 1 and 2, 5.38 mmol, approximately 20-25 mole % of the totalmonomer composition; Example 3, 8.44 mmol, approximately 31-39 mole % ofthe total monomer composition; and Example 4, 12.31 mmol, approximately46-57 mole % of the total monomer composition. The reactions werecarried out at low to moderate temperature and pressure, i.e., 0 to 50°C. and less than 100 psi. Examples 5 and 6 describe copolymerization ofethylene with a diolefin containing an enol ether linkage and ananhydride linkage, respectively, with the hydrolyzable comonomer inExample 5 representing approximately 27-34 mole % of the total monomercomposition (7.5 mmol) and the hydrolyzable comonomer in Example 6representing approximately 20-24 mole % of the total monomer composition(5.25 mmol).

EXAMPLE 1 Preparation ofEthylene/3,9-Divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane Copolymer Usinga Zirconium Metallocene complex as Catalyst

This example describes copolymerization of ethylene with3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane, i.e., a hydrolyzablecomonomer containing a hydrolytically cleavable bicyclic acetal linkage,the comonomer having the structure

using a metallocene catalyst. The catalyst used was(CH₃)₂Si(C₁₆H₁₂)₂ZrCl₂ (molecular weight 628.83, available from Hoechst;C₁₆H₁₂≡2-methyl-4-phenylindenyl), the molecular structure of which is asfollows:

A glass reactor was flushed with argon and charged with 100 mL oftoluene and 1.0 g (5.38 mmol) of3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane. The reactor was thenflushed with ethylene, and the solution was stirred with an overheadmechanical stirrer. A solution of 0.5 g TMA (trimethylaluminum)-free MAO(methyl aluminoxane) in 2 mL toluene was added, and the reactor waspressurized with ethylene to 25 psi for 1 minute. The pressure wasreleased, and a catalyst/MAO mixture, prepared from 0.5 g TMA-free MAOin 2 mL of toluene and 0.013 mmoles of (CH₃)₂Si(C₁₆H₁₂)₂ZrCl₂ was added.The reactor was then pressurized to 45 psi ethylene and isolated fromthe ethylene supply. The pressure drop was monitored over the next twohours (reaction carried out at about 20° C.) and observed to drop by 16psi. When little further pressure drop was detected, at about 100 min,the reaction was quenched with 2×10 mL methanol. The copolymer wasisolated by filtration, washed with methanol, and dried under vacuum for16 hours to give 1.27 g of a powdery solid.

¹H NMR of the copolymer and the hydrolyzable divinyl-tetraoxaspiroundecane monomer established the incorporation of the hydrolyzablemonomer in the copolymer (FIGS. 1-2). Based on the NMR data, thestructure of the copolymer appeared to be that of a single strandedpolyethylene chain with incorporation of the comonomer primarily as achain extender (i.e., contained within the backbone of the copolymer)with some degree of monofunctional incorporation (i.e., as a short sidechain).

The NMR analysis clearly showed incorporation of the monomer, estimated,from integration of the peaks, to be about 20 mole %. Although somedegree of crosslinking could not be ruled out, gel permeationchromatography (GPC) did not give any evidence of significantcrosslinking in these samples.

Molecular weight determination: The copolymerization procedure wasrepeated, and the molecular weights of the products obtained from theinitial copolymerization reaction and the repeated copolymerizationreaction were then estimated via gel permeation chromatography (GPC),using as standards a 106,096 M_(w) polyethylene and a 52,497 M_(w)polyethylene. Each analysis gave a single peak. The first sample gave anM_(n) of 53,787 and an M_(w) of 172,503; the second sample gave a anM_(n) of 64,260 and an M_(w) of 139,782.

EXAMPLE 2 Preparation ofEthylene/3,9-Divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane Copolymer Usinga Titanium Metallocene complex as Catalyst

The reaction of Example 1 was repeated using 0.0123 mmol of a titaniummetallocene complex as the reaction catalyst. The catalyst was(CH₃)₂Si(1,2,3,4-tetramethyl cyclopentadiene)(t-Bu)TiCl₂ (Dow), themolecular structure of which is as follows:

The copolymer was isolated by filtration, washed with methanol, anddried under vacuum for 16 hours to give 1.3 g of a powdery solid.

EXAMPLE 3 Preparation of Ethylene/Diallyltetramethyldisloxane Copolymer

This example describes copolymerization of ethylene withdiallyldimethyllsiloxane, a hydrolyzable comonomer containing ahydrolytically cleavable siloxane linkage, the comonomer having thestructure

using the metallocene catalyst of Example 1.

A glass reactor fitted with an overhead stirrer was charged with 100 mLof toluene and 1.52 g (8.44 mmol) of diallyldimethylsiloxane. Thereactor was then purged and degassed by repeated cycles of pressurizingwith argon to 25 psig and evacuation under vacuum. A solution of 0.5 gof TMA-free MAO in 2 mL of toluene was added under argon and the reactorpressurized with ethylene to 25 psig for 1 minute. The pressure wasreleased and a catalyst/MAO mixture, prepared from a freshly preparedmixture of 0.5 g of TMA-free MAO in 2 mL of toluene and 0.0175 mmoles ofcatalyst in 3 mL of toluene was added.

The reactor was then pressurized to 45 psi ethylene and isolated fromthe ethylene supply. The pressure drop was monitored over the next twohours (reaction carried out at room temperature) and ethylene pressurewas observed to rapidly drop. The reaction was allowed to continue for1.5 hours at which time the pressure had dropped to approximately 5 psi.The reaction was quenched with 2×10 mL methanol. The polymer wasisolated by filtration, washed with methanol, and dried until constantweight to give 2.69 g of a white solid.

EXAMPLE 4 Preparation of Ethylene/tetraallyloxysilane Copolymer

This example describes copolymerization of ethylene withtetraallyloxysilane, a hydrolyzable comonomer containing hydrolyticallycleavable siloxane linkages, the comonomer having the structure

using the metallocene catalyst of Example 1.

A glass reactor fitted with an overhead stirrer was charged with 100 mLof toluene and 2.98 g (11.64 mmol) of tetrallyloxysilane. The reactorwas then purged and degassed by repeated cycles of pressurizing withargon to 25 psig and evacuation under vacuum. A solution of 0.5 g ofTMA-free MAO (methyl aluminoxane) in 2 mL of toluene was added underargon and the reactor pressurized with ethylene to 25 psig for 1 minute.The pressure was released and a catalyst /MAO mixture, prepared from afreshly prepared mixture of 0.5 g of TMA-free MAO in 2 mL of toluene and0.0159 mmoles of catalyst in 3 mL of toluene was added.

The reactor was then pressurized to 45 psig of ethylene and isolatedfrom the ethylene supply. The pressure drop was monitored over the nexttwo hours (reaction carried out at room temperature). The reaction wasallowed to continue for 1.5 hours at which time the pressure had droppedto approximately 5 psi. The reaction was quenched with 2×10 mL methanol.The polymer was isolated by filtration, washed with methanol, and drieduntil constant weight to give 1.07 g of a white solid.

EXAMPLE 5 Preparation of Ethylene/1-Allyloxy-Penta-1,4-Diene Copolymer

This example describes copolymerization of ethylene with1-allyloxy-penta-1,4-diene, a hydrolyzable comonomer containing ahydrolytically cleavable enol ether linkage, the comonomer having thestructure

using the metallocene catalyst of Example 2.

A glass reactor fitted with an overhead stirrer is charged with 100 mLof toluene and 0.915 g (7.5 mmol) of 1-allyloxy-penta-1,4-diene. Thereactor is then purged and degassed by repeated cycles of pressurizingwith argon to 25 psig and evacuation under vacuum. A solution of 0.5 gof TMA-free MAO in 2 mL of toluene is added under argon and the reactorpressurized with ethylene to 25 psig for 1 minute. The pressure isreleased and a catalyst/MAO mixture, prepared from a freshly preparedmixture of 0.5 g of TMA-free MAO in 2 mL of toluene and 0.010 mmoles ofcatalyst in 3 mL of toluene is added.

The reactor is then pressurized to 45 psi ethylene and isolated from theethylene supply. The pressure drop is monitored over the next two hours(reaction carried out at room temperature) and ethylene pressure isobserved to rapidly drop. The reaction is allowed to continue for 1.5hours at which time the pressure drops to approximately 5 psi. Thereaction is quenched with 2×10 mL methanol. The polymer may be isolatedby filtration, washed with methanol, and dried until constant weight togive the desired copolymer.

EXAMPLE 6 Preparation of Ethylene/Anhydride Copolymer

This example describes copolymerization of ethylene with a hydrolyzablecomonomer containing a hydrolytically cleavable anhydride linkage, thecomonomer having the structure

using the diimine catalyst [Ar—N═C(CH₃)—C(CH₃)═N—Ar]PdCl₂, wherein Ar is2,4,6-triisopropyl-phenyl, having the molecular structure

Methylene chloride (150 mL) is placed in a 300-mL glass reactor, whichis then flushed and charged with ethylene to a pressure of 15 psig. Thesolution is allowed to equilibrate at room temperature for 15 min, andthen a solution of catalyst (approximately 0.01 mmol) and 0.81 g (5.25mmol) anhydride in methylene chloride is added. A solution of sodiumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBAF; 1 eq) inmethylene chloride (10 mL) is injected into the reactor with argonoverpressure to form the active catalyst in situ and initiatepolymerization. After the desired time period, an aliquot is removed andevaporated to dryness. The sample is analyzed by ¹H NMR, and the NMRspectrum confirms the incorporation of both monomers in the copolymerproduct.

EXAMPLE 7 Hydrolysis of Copolymers

Three 0.2 g samples of each of the copolymers prepared in Examples 1 and2 were placed in 10 ml of pH 4, pH 7 and pH 10 buffer solutions. The sixsolutions were stirred for 18 hours at ambient temperature. Afterstirring the samples were centrifuged for 5 minutes and the liquiddecanted off. The samples were transferred into vials and driedovernight in a vacuum oven. The samples were then weighed. The resultsare presented in Table 1 and in FIG. 3.

TABLE 1 Copolymer wt. (g) Copolymer wt. (g) Percent Dissolution pHExample 1 Example 2 Example 1 Example 2 4 0.134 0.131 33.0% 34.5% 70.125 0.132 37.5% 34.0% 10 0.125 0.110 37.5% 45.0%

The hydrolysis data in Table 1 and FIG. 3 and the NMR spectra of FIGS. 1and 2 indicate that the invention provides olefin copolymers in whichthe amount of a polar, hydrolyzable monomer that can be incorporated issubstantially increased relative to copolymers synthesized using priorart methods. For example, the process described by Austin et al., inInternational Patent Publication No. WO 92/12185, using aradical-initiated ring-opening copolymerization reaction betweenethylene and a cyclic ketene acetal, 2-methylene-1,3-dioxepane (MDOP),results in a polyester containing only 3.20 mole % of the “hydrolyzable”monomer, even when the level of MDOP in the feed was 25 wt. %. Bycontrast, 20 mole % incorporation was achieved in the copolymer ofExample 1.

Samples (0.2 g aliquots) of the copolymers prepared in Examples 3 and 4were evaluated as above, at various pH levels. After treatment themixtures were filtered and washed with water and oven dried untilconstant weight. The results are presented in Table 2.

TABLE 2 Weight Percent pH Example Recovered (g) Dissolution 4 3 0.200 07 3 0.200 0 10 3 0.200 0 13 3 0.183 8.5 14 3 0.153 23.5 4 4 0.130 35.0 74 0.162 19.0 10 4 0.157 21.5

The data in Table 2 indicate that a higher pH may be required to effecthydrolysis of certain copolymers, and that variations in copolymerstructure can provide a higher or lower degree of hydrolysis. Thesiloxane copolymer prepared from the tetraolefin of Example 4 resultedin greater dissolution upon hydrolysis at pH 4, 7, and 10, while thesiloxane copolymer of Example 3, prepared from the correspondingdiolefin, required a higher pH to effect significant hydrolysis.

1. A degradable olefin copolymer prepared by addition polymerization, inthe presence of a catalytically effective amount of a metallocenecomplex of a Group 4, 5, or 6 transition metal and a catalyst activatorthat renders the complex cationic or zwitterionic, of a monomer mixturecontaining at most 80 mole % of at least one nonhydrolyzable olefinmonomer and at least 20 mole % of a diolefin monomer containing ahydrolytically cleavable linkage selected from a cyclic acetal linkageand an ester linkage.
 2. The copolymer of claim 1, wherein thehydrolytically cleavable linkage is a cyclic acetal linkage.
 3. Thecopolymer of claim 1, wherein the hydrolytically cleavable linkage is anester linkage.
 4. A blend comprising the degradable copolymer of claim 1and at least one additional polymer.
 5. The blend of claim 4, whereinthe additional polymer is a degradable polymer.
 6. The blend of claim 5,wherein the additional polymer is a hydrolyzable polymer.
 7. The blendof claim 4, wherein the additional polymer is a nonhydrolyzable polymer.8. The blend of claim 6, further including a nondegradable polymer.
 9. Ablend comprising about 5 wt. % to about 99 wt. % of a mixture ofdegradable polymers and about 1 wt. % to 95 wt. % of a nondegradablepolymer, wherein the mixture of degradable polymers is composed of about30 wt. % to about 95 wt. % of the copolymer of claim 1 and about 5 wt. %to about 70 wt. % of at least one additional degradable polymer.
 10. Theblend of claim 9, wherein the at least one additional degradable polymerincludes starch.
 11. The blend of claim 10, wherein the nondegradablepolymer is selected from low density polyethylene, high densitypolyethylene, linear low density polyethylene, ethylene-propylenerubber, polystyrene, polyvinylchloride, polyhalocarbons,polychloroprene, polybutadiene, polyisoprene, polyisobutylene,nitrile-butadiene rubber, styrene-butadiene rubber, chlorinatedpolyethylene, clilorosulfonated polyethylene, epichlorohydrin rubber,butyl rubber, halobutyl rubber, copolymers of ethylene with propylene,isobutene, butene, hexene, octene, vinyl chloride, vinyl alcohol, andcombinations thereof.
 12. A degradable article at least partiallycomprising a degradable copolymer composed of at most 80 mole % ofnonhydrolyzable monomer units resulting from polymerization ofnonhydrolyzable olefin monomers, and at least 20 mole % of hydrolyzablemonomer units resulting from polymerization of hydrolyzable olefinmonomers containing at least one linkage that is hydrolyticallycleavable under acidic or basic conditions, A degradable article atleast partially comprising a degradable copolymer composed of at most 80mole % of nonhydrolyzable monomer units resulting from polymerization ofnonhydrolyzable olefin monomers, and at least 20 mole % of hydrolyzablemonomer units resulting from polymerization of hydrolyzable olefinmonomers containing at least one linkage that is hydrolyticallycleavable under acidic or basic conditions, wherein: the nonhydrolyzableolefin monomers are addition polymerizable monomers of the formR¹CH═CHR², wherein R¹ is hydrido, C₁-C₂₄ alkyl, substituted C₁-C₂₄alkyl, C₁-C₂₄ heteroalkyl, or substituted C₁-C₂₄ heteroalkyl, and R² ishydrido, C₁-C₂₄ alkyl, substituted C₁-C₂₄ alkyl, C₁-C₂₄ heteroalkyl,substituted C₁-C₂₄ heteroalkyl, C₂-C₂₄ alkenyl, substituted C₂-C₂₄alkenyl, C₂-C₂₄ heteroalkenyl, substituted C₂-C₂₄ heteroalkenyl, C₅-C₂₄aryl, substituted C₅-C₂₄ aryl, C₅-C₂₄ heteroaryl, substituted C₅-C₂₄heteroaryl, C₆-C₂₄ alkaryl, substituted and/or heteroatom-containingC₆-C₂₄ alkaryl, or halo, or wherein R¹ and R² are linked to form acyclic group; and the hydrolyzable olefin monomers are additionpolymerizable monomers of the form R³CH═CH-(L¹)_(m)-X-(L²)_(n)-CH═CHR⁴wherein R³ and R⁴ are independently hydrido, C₁-C₂₄ alkyl, substitutedC₁-C₂₄ alkyl, C₁-C₂₄ heteroalkyl, substituted C₁-C₂₄ heteroalkyl, C₅-C₂₄aryl, substituted C₅-C₂₄ aryl, C₅-C₂₄ heteroaryl, or substituted C₅-C₂₄heteroaryl, m and n are independently zero or 1, L¹ and L² areoptionally substituted and/or heteroatom-containing hydrocarbylene, andX is a hydrolytically cleavable linkage.
 13. The article of claim 12,wherein: R¹ is hydrido or C₁-C₁₂ alkyl; and R² is hydrido, C₁-C₁₂ alkyl,substituted C₁-C₁₂ alkyl, C₁-C₁₂ heteroalkyl, substituted C₁-C₁₂heteroalkenyl, C₂-C₁₂ alkenyl, substituted C₂-C₁₂ alkenyl, C₂-C₁₂heteroalkenyl, substituted C₂-C₁₂ heteroalkenyl, C₅-C₁₄ aryl,substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl, substituted C₅-C₁₄heteroaryl, C₆-C₁₆ alkaryl, substituted and/or heteroatom-containingC₆-C₁₆ alkaryl, or halo, or wherein R¹ and R² are linked to form abridge -Q- wherein Q is a three-atom to seven-atom hydrocarbylenespacer; R³ and R⁴ are independently hydrido, C₁-C₁₂ alkyl, substitutedC₁-C₁₂ alkyl, C₁-C₁₂ heteroalkyl, substituted C₁-C₁₂ heteroalkyl, C₅-C₁₄aryl, substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl, or substituted C₅-C₁₄heteroaryl; L¹ and L² are independently lower alkylene optionallysubstituted and/or containing a hydrolytically cleavable linkage; and Xis selected from —(CO)—O—, —CH═CH—O—, —O—CR₂—O—, —CH(OH)—O—,—(CO)—O—(CO)—, —O—(CO)—O), —(CO)—NR—, —O—(CO)—NR—, —CH₂—NR—, —CHR—NR—,—CR₂—NR—, —CH═N—, —CR═N—, —Cy¹(═O)—, —Cy²—, —NR—NR—, —Cy³Cy⁴—, —(CO)—S—,—P(O)(OR)—O—, —SO₂—OR—, —C(OR)₂—O—, —O—, —S—, —S—S—, —SiR′R″—O——SiR′R″—, —O— SiR′R″—O—, —SiR′R″—NR— SiR′R″—, and —NR— SiR′R″—NR—),wherein R is optionally substituted and/or heteroatom-containing C₁-C₁₂hydrocarbyl, R′ and R″ are independently selected from hydrido andoptionally substituted and/or heteroatom-containing C₁-C₁₂ hydrocarbyl,Cy¹ is a nitrogen containing heterocycle, Cy² is a five- or six-memberedring containing a —CH═N— linkage, and Cy³ and Cy⁴ are five- orsix-membered rings each containing an acetal linkage.
 14. The article ofclaim 13, wherein: R¹ is hydrido or lower alkyl; R² is hydrido, loweralkyl, substituted lower alkyl, lower heteroalkyl, substituted lowerheteroalkyl, C₅-C₁₄ aryl, substituted C₅-C₁₄ aryl, C₅-C₁₄ heteroaryl,substituted C₅-C₁₄ heteroaryl, C₆-C₁₆ alkaryl, substituted and/orheteroatom-containing C₆-C₁₆ alkaryl, or halo; R³ and R⁴ areindependently hydrido or lower alkyl; L¹ and L² are independently loweralkylene optionally substituted with an allyl group; R is lower alkyl;and R′ and R″ are selected from hydrido, lower alkyl, and lower alkoxy.15. The article of claim 14, wherein R³ and R⁴ are hydrido and L¹ and L²are unsubstituted lower alkylene.
 16. The article of claim 14, whereinR³ and R⁴ are hydrido and m and n are zero.
 17. A composition forpreparing a degradable article, comprising the degradable copolymer ofclaim 1 and at least one additive selected from additional degradablecomponents, nondegradable polymers, anti-oxidants, pro-oxidants,stability enhancers, tensile strength enhancers, photosensitizers,colorants, plasticizers, tackifiers, fillers, antistatic agents, flameretardants, and opacifiers.